Merge feature/v1.3.2-lint-cleanup into main

- Complete lint cleanup (Phase 1-7)
- Replace magic numbers with constants
- Remove unused imports/members
- Add Logger.w() for swallowed exceptions
- Custom SyncException for better error handling
- ConstructorParameterNaming with @SerializedName
- ReturnCount & Destructuring with @Suppress
- F-Droid: Add privacy notice for file logging
- Update docs (FEATURES.md, README.md)
- Add fastlane changelogs for versionCode 10

.github/workflows/build-production-apk.yml

@@ -61,33 +61,15 @@ jobs:
         run: |
           mkdir -p apk-output
           
-          # === Standard Flavor (mit Google Services) ===
-          # Universal APK (funktioniert auf allen Geraeten)
-          cp android/app/build/outputs/apk/standard/release/app-standard-universal-release.apk \
-             apk-output/simple-notes-sync-v${{ env.VERSION_NAME }}-standard-universal.apk
+          # Standard Flavor - Universal APK
+          cp android/app/build/outputs/apk/standard/release/app-standard-release.apk \
+             apk-output/simple-notes-sync-v${{ env.VERSION_NAME }}-standard.apk
           
-          # ARM64 APK (moderne Geräte 2018+)
-          cp android/app/build/outputs/apk/standard/release/app-standard-arm64-v8a-release.apk \
-             apk-output/simple-notes-sync-v${{ env.VERSION_NAME }}-standard-arm64-v8a.apk
+          # F-Droid Flavor - Universal APK
+          cp android/app/build/outputs/apk/fdroid/release/app-fdroid-release.apk \
+             apk-output/simple-notes-sync-v${{ env.VERSION_NAME }}-fdroid.apk
           
-          # ARMv7 APK (ältere Geräte)
-          cp android/app/build/outputs/apk/standard/release/app-standard-armeabi-v7a-release.apk \
-             apk-output/simple-notes-sync-v${{ env.VERSION_NAME }}-standard-armeabi-v7a.apk
-          
-          # === F-Droid Flavor (ohne Google Services) ===
-          # Universal APK
-          cp android/app/build/outputs/apk/fdroid/release/app-fdroid-universal-release.apk \
-             apk-output/simple-notes-sync-v${{ env.VERSION_NAME }}-fdroid-universal.apk
-          
-          # ARM64 APK
-          cp android/app/build/outputs/apk/fdroid/release/app-fdroid-arm64-v8a-release.apk \
-             apk-output/simple-notes-sync-v${{ env.VERSION_NAME }}-fdroid-arm64-v8a.apk
-          
-          # ARMv7 APK
-          cp android/app/build/outputs/apk/fdroid/release/app-fdroid-armeabi-v7a-release.apk \
-             apk-output/simple-notes-sync-v${{ env.VERSION_NAME }}-fdroid-armeabi-v7a.apk
-          
-          echo "✅ APK-Dateien vorbereitet (Standard + F-Droid):"
+          echo "✅ APK-Dateien vorbereitet:"
           ls -lh apk-output/
       
       - name: APK-Artefakte hochladen
@@ -138,14 +120,8 @@ jobs:
             
             | Variante | Datei | Info |
             |----------|-------|------|
-            | **🏆 Empfohlen** | `simple-notes-sync-v${{ env.VERSION_NAME }}-standard-universal.apk` | Funktioniert auf allen Android-Geraeten |
-            | Modern (2018+) | `simple-notes-sync-v${{ env.VERSION_NAME }}-standard-arm64-v8a.apk` | Kleinere Dateigröße fuer 64-bit Geräte |
-            | Aelter (<2018) | `simple-notes-sync-v${{ env.VERSION_NAME }}-standard-armeabi-v7a.apk` | Fuer 32-bit ARM Geräte |
-            | F-Droid Universal | `simple-notes-sync-v${{ env.VERSION_NAME }}-fdroid-universal.apk` | Fuer F-Droid Store |
-            | F-Droid ARM64 | `simple-notes-sync-v${{ env.VERSION_NAME }}-fdroid-arm64-v8a.apk` | F-Droid 64-bit |
-            | F-Droid ARMv7 | `simple-notes-sync-v${{ env.VERSION_NAME }}-fdroid-armeabi-v7a.apk` | F-Droid 32-bit |
-            
-            💡 **Nicht sicher?** → Nimm die **Universal** APK!
+            | **🏆 Empfohlen** | `simple-notes-sync-v${{ env.VERSION_NAME }}-standard.apk` | Standard-Version (funktioniert auf allen Geraeten) |
+            | F-Droid | `simple-notes-sync-v${{ env.VERSION_NAME }}-fdroid.apk` | Fuer F-Droid Store |
             
             ---
             

CHANGELOG.md

@@ -6,6 +6,130 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 
 ---
 
+## [1.3.2] - 2026-01-10
+
+### Changed
+- **🧹 Code-Qualität: "Clean Slate" Release**
+  - Alle einfachen Lint-Issues behoben (Phase 1-7 des Cleanup-Plans)
+  - Unused Imports und Members entfernt
+  - Magic Numbers durch benannte Konstanten ersetzt
+  - SwallowedExceptions mit Logger.w() versehen
+  - MaxLineLength-Verstöße reformatiert
+  - ConstructorParameterNaming (snake_case → camelCase mit @SerializedName)
+  - Custom Exceptions: SyncException.kt und ValidationException.kt erstellt
+
+### Added  
+- **📝 F-Droid Privacy Notice**
+  - Datenschutz-Hinweis für die Datei-Logging-Funktion
+  - Erklärt dass Logs nur lokal gespeichert werden
+  - Erfüllt F-Droid Opt-in Consent-Anforderungen
+
+### Technical Improvements
+- **⚡ Neue Konstanten für bessere Wartbarkeit**
+  - `SYNC_COMPLETED_DELAY_MS`, `ERROR_DISPLAY_DELAY_MS` (MainActivity)
+  - `CONNECTION_TIMEOUT_MS` (SettingsActivity)
+  - `SOCKET_TIMEOUT_MS`, `MAX_FILENAME_LENGTH`, `ETAG_PREVIEW_LENGTH` (WebDavSyncService)
+  - `AUTO_CANCEL_TIMEOUT_MS` (NotificationHelper)
+  - RFC 1918 IP-Range Konstanten (UrlValidator)
+  - `DAYS_THRESHOLD`, `TRUNCATE_SUFFIX_LENGTH` (Extensions)
+
+- **🔒 @Suppress Annotations für legitime Patterns**
+  - ReturnCount: Frühe Returns für Validierung sind idiomatisch
+  - LoopWithTooManyJumpStatements: Komplexe Sync-Logik dokumentiert
+
+### Notes
+- Komplexe Refactorings (LargeClass, LongMethod) für v1.3.3+ geplant
+- Deprecation-Warnungen (LocalBroadcastManager, ProgressDialog) bleiben bestehen
+
+---
+
+## [1.3.1] - 2026-01-08
+
+### Fixed
+- **🔧 Multi-Device JSON Sync (Danke an Thomas aus Bielefeld)**
+  - JSON-Dateien werden jetzt korrekt zwischen Geräten synchronisiert
+  - Funktioniert auch ohne aktiviertes Markdown
+  - Hybrid-Optimierung: Server-Timestamp (Primary) + E-Tag (Secondary) Checks
+  - E-Tag wird nach Upload gecached um Re-Download zu vermeiden
+
+### Performance Improvements
+- **⚡ JSON Sync Performance-Parität**
+  - JSON-Sync erreicht jetzt gleiche Performance wie Markdown (~2-3 Sekunden)
+  - Timestamp-basierte Skip-Logik für unveränderte Dateien (~500ms pro Datei gespart)
+  - E-Tag-Matching als Fallback für Dateien die seit letztem Sync modifiziert wurden
+  - **Beispiel:** 24 Dateien von 12-14s auf ~2.7s reduziert (keine Änderungen)
+
+- **⏭️ Skip unveränderte Dateien** (Haupt-Performance-Fix!)
+  - JSON-Dateien: Überspringt alle Notizen, die seit letztem Sync nicht geändert wurden
+  - Markdown-Dateien: Überspringt unveränderte MD-Dateien basierend auf Server-Timestamp
+  - **Spart ~500ms pro Datei** bei Nextcloud (~20 Dateien = 10 Sekunden gespart!)
+  - Von 21 Sekunden Sync-Zeit auf 2-3 Sekunden reduziert
+
+- **⚡ Session-Caching für WebDAV** 
+  - Sardine-Client wird pro Sync-Session wiederverwendet (~600ms gespart)
+  - WiFi-IP-Adresse wird gecacht statt bei jeder Anfrage neu ermittelt (~300ms gespart)
+  - `/notes/` Ordner-Existenz wird nur einmal pro Sync geprüft (~500ms gespart)
+  - **Gesamt: ~1.4 Sekunden zusätzlich gespart**
+
+- **📝 Content-basierte Markdown-Erkennung**
+  - Extern bearbeitete Markdown-Dateien werden auch erkannt wenn YAML-Timestamp nicht aktualisiert wurde
+  - Löst das Problem: Obsidian/Texteditor-Änderungen wurden nicht importiert
+  - Hybridansatz: Erst Timestamp-Check (schnell), dann Content-Vergleich (zuverlässig)
+
+### Added
+- **🔄 Sync-Status-Anzeige (UI)**
+  - Sichtbares Banner "Synchronisiere..." mit ProgressBar während Sync läuft
+  - Sync-Button und Pull-to-Refresh werden deaktiviert während Sync aktiv
+  - Verhindert versehentliche Doppel-Syncs durch visuelle Rückmeldung
+  - Auch in Einstellungen: "Jetzt synchronisieren" Button wird deaktiviert
+
+### Fixed
+- **🔧 Sync-Mutex verhindert doppelte Syncs**
+  - Keine doppelten Toast-Nachrichten mehr bei schnellem Pull-to-Refresh
+  - Concurrent Sync-Requests werden korrekt blockiert
+
+- **🐛 Lint-Fehler behoben**
+  - `View.generateViewId()` statt hardcodierte IDs in RadioButtons
+  - `app:tint` statt `android:tint` für AppCompat-Kompatibilität
+
+### Added
+- **🔍 detekt Code-Analyse**
+  - Statische Code-Analyse mit detekt 1.23.4 integriert
+  - Pragmatische Konfiguration für Sync-intensive Codebasis
+  - 91 Issues identifiziert (als Baseline für v1.4.0)
+
+- **🏗️ Debug Build mit separatem Package**
+  - Debug-APK kann parallel zur Release-Version installiert werden
+  - Package: `dev.dettmer.simplenotes.debug` (Debug) vs `dev.dettmer.simplenotes` (Release)
+  - App-Name zeigt "Simple Notes (Debug)" für einfache Unterscheidung
+
+- **📊 Debug-Logging UI**
+  - Neuer "Debug Log" Button in Einstellungen → Erweitert
+  - Zeigt letzte Sync-Logs mit Zeitstempeln
+  - Export-Funktion für Fehlerberichte
+
+### Technical
+- `WebDavSyncService`: Hybrid-Optimierung für JSON-Downloads (Timestamp PRIMARY, E-Tag SECONDARY)
+- `WebDavSyncService`: E-Tag refresh nach Upload statt Invalidierung (verhindert Re-Download)
+- E-Tag Caching: `SharedPreferences` mit Key-Pattern `etag_json_{noteId}`
+- Skip-Logik: `if (serverModified <= lastSync) skip` → ~1ms pro Datei
+- Fallback E-Tag: `if (serverETag == cachedETag) skip` → für Dateien modifiziert nach lastSync
+- PROPFIND nach PUT: Fetch E-Tag nach Upload für korrektes Caching
+- `SyncStateManager`: Neuer Singleton mit `StateFlow<Boolean>` für Sync-Status
+- `MainActivity`: Observer auf `SyncStateManager.isSyncing` für UI-Updates
+- Layout: `sync_status_banner` mit `ProgressBar` + `TextView`
+- `WebDavSyncService`: Skip-Logik für unveränderte JSON/MD Dateien basierend auf `lastSyncTimestamp`
+- `WebDavSyncService`: Neue Session-Cache-Variablen (`sessionSardine`, `sessionWifiAddress`, `notesDirEnsured`)
+- `getOrCreateSardine()`: Cached Sardine-Client mit automatischer Credentials-Konfiguration
+- `getOrCacheWiFiAddress()`: WiFi-Adresse wird nur einmal pro Sync ermittelt
+- `clearSessionCache()`: Aufräumen am Ende jeder Sync-Session
+- `ensureNotesDirectoryExists()`: Cached Directory-Check
+- Content-basierter Import: Vergleicht MD-Content mit lokaler Note wenn Timestamps gleich
+- Build-Tooling: detekt aktiviert, ktlint vorbereitet (deaktiviert wegen Parser-Problemen)
+- Debug BuildType: `applicationIdSuffix = ".debug"`, `versionNameSuffix = "-debug"`
+
+---
+
 ## [1.3.0] - 2026-01-07
 
 ### Added

README.en.md

@@ -85,7 +85,7 @@ cd android
 ./gradlew assembleStandardRelease
 ```
 
-➡️ **Build guide:** [DOCS.en.md](docs/DOCS.en.md)
+➡️ **Build guide:** [DOCS.en.md](docs/DOCS.en.md#-build--deployment)
 
 ---
 
@@ -101,4 +101,4 @@ MIT License - see [LICENSE](LICENSE)
 
 ---
 
-**v1.2.1** · Built with ❤️ using Kotlin + Material Design 3
+**v1.3.2** · Built with ❤️ using Kotlin + Material Design 3

README.md

@@ -88,7 +88,7 @@ cd android
 ./gradlew assembleStandardRelease
 ```
 
-➡️ **Build-Anleitung:** [DOCS.md](docs/DOCS.md)
+➡️ **Build-Anleitung:** [DOCS.md](docs/DOCS.md#-build--deployment)
 
 ---
 
@@ -104,4 +104,4 @@ MIT License - siehe [LICENSE](LICENSE)
 
 ---
 
-**v1.2.1** · Built with ❤️ using Kotlin + Material Design 3
+**v1.3.2** · Built with ❤️ using Kotlin + Material Design 3

android/.editorconfig

@@ -0,0 +1,61 @@
+# ⚡ v1.3.1: EditorConfig for ktlint
+# https://editorconfig.org
+
+root = true
+
+[*]
+charset = utf-8
+end_of_line = lf
+indent_size = 4
+indent_style = space
+insert_final_newline = true
+max_line_length = 120
+trim_trailing_whitespace = true
+
+[*.{kt,kts}]
+# ktlint rules
+ktlint_code_style = android_studio
+ktlint_standard_no-wildcard-imports = disabled
+ktlint_standard_package-name = enabled
+ktlint_standard_filename = enabled
+ktlint_standard_class-naming = enabled
+ktlint_standard_function-naming = enabled
+ktlint_standard_property-naming = enabled
+ktlint_standard_backing-property-naming = enabled
+ktlint_standard_enum-entry-name-case = enabled
+ktlint_standard_multiline-if-else = enabled
+ktlint_standard_no-empty-class-body = enabled
+ktlint_standard_no-empty-first-line-in-class-body = enabled
+ktlint_standard_blank-line-before-declaration = enabled
+ktlint_standard_context-receiver-wrapping = enabled
+ktlint_standard_function-expression-body = disabled
+ktlint_standard_function-literal = enabled
+ktlint_standard_function-type-modifier-spacing = enabled
+ktlint_standard_kdoc-wrapping = enabled
+ktlint_standard_modifier-list-spacing = enabled
+ktlint_standard_no-blank-line-in-list = enabled
+ktlint_standard_no-consecutive-comments = disabled
+ktlint_standard_no-single-line-block-comment = enabled
+ktlint_standard_parameter-list-spacing = enabled
+ktlint_standard_parameter-list-wrapping = enabled
+ktlint_standard_property-wrapping = enabled
+ktlint_standard_spacing-between-function-name-and-opening-parenthesis = enabled
+ktlint_standard_statement-wrapping = enabled
+ktlint_standard_string-template-indent = disabled
+ktlint_standard_try-catch-finally-spacing = enabled
+ktlint_standard_type-argument-list-spacing = enabled
+ktlint_standard_type-parameter-list-spacing = enabled
+ktlint_standard_value-argument-comment = enabled
+ktlint_standard_value-parameter-comment = enabled
+
+[*.md]
+trim_trailing_whitespace = false
+
+[*.{xml,json}]
+indent_size = 2
+
+[*.yml]
+indent_size = 2
+
+[Makefile]
+indent_style = tab

android/app/build.gradle.kts

@@ -1,6 +1,9 @@
 plugins {
     alias(libs.plugins.android.application)
     alias(libs.plugins.kotlin.android)
+    // ⚡ v1.3.1: ktlint deaktiviert wegen Parser-Problemen, aktivieren in v1.4.0
+    // alias(libs.plugins.ktlint)
+    alias(libs.plugins.detekt)
 }
 
 import java.util.Properties
@@ -17,8 +20,8 @@ android {
         applicationId = "dev.dettmer.simplenotes"
         minSdk = 24
         targetSdk = 36
-        versionCode = 8  // 🚀 v1.3.0: Multi-Device Sync with deletion tracking
-        versionName = "1.3.0"  // 🚀 v1.3.0: Multi-Device Sync, E-Tag caching, Markdown auto-import
+        versionCode = 10  // 🚀 v1.3.2: Lint-Cleanup "Clean Slate"
+        versionName = "1.3.2"  // 🚀 v1.3.2: Code-Qualität-Release (alle einfachen Lint-Issues behoben)
 
         testInstrumentationRunner = "androidx.test.runner.AndroidJUnitRunner"
         
@@ -32,23 +35,15 @@ android {
         includeInBundle = false  // Also disable for AAB (Google Play)
     }
     
-    // Enable multiple APKs per ABI for smaller downloads
-    splits {
-        abi {
-            isEnable = true
-            reset()
-            include("armeabi-v7a", "arm64-v8a")
-            isUniversalApk = true  // Also generate universal APK
-        }
-    }
-    
     // Product Flavors for F-Droid and standard builds
+    // Note: APK splits are disabled to ensure single APK output
     flavorDimensions += "distribution"
     productFlavors {
         create("fdroid") {
             dimension = "distribution"
             // F-Droid builds have no proprietary dependencies
             // All dependencies in this project are already FOSS-compatible
+            // No APK splits - F-Droid expects single universal APK
         }
         
         create("standard") {
@@ -75,6 +70,16 @@ android {
     }
 
     buildTypes {
+        debug {
+            // ⚡ v1.3.1: Debug-Builds können parallel zur Release-App installiert werden
+            applicationIdSuffix = ".debug"
+            versionNameSuffix = "-debug"
+            isDebuggable = true
+            
+            // Optionales separates Icon-Label für Debug-Builds
+            resValue("string", "app_name_debug", "Simple Notes (Debug)")
+        }
+        
         release {
             isMinifyEnabled = true
             isShrinkResources = true
@@ -144,3 +149,27 @@ fun getBuildDate(): String {
     val dateFormat = SimpleDateFormat("yyyy-MM-dd", Locale.US)
     return dateFormat.format(Date())
 }
+
+// ⚡ v1.3.1: ktlint deaktiviert wegen Parser-Problemen
+// Aktivieren in v1.4.0 wenn Code-Stil bereinigt wurde
+// ktlint {
+//     android = true
+//     outputToConsole = true
+//     ignoreFailures = true
+//     enableExperimentalRules = false
+//     filter {
+//         exclude("**/generated/**")
+//         exclude("**/build/**")
+//     }
+// }
+
+// ⚡ v1.3.1: detekt-Konfiguration
+detekt {
+    buildUponDefaultConfig = true
+    allRules = false
+    config.setFrom(files("$rootDir/config/detekt/detekt.yml"))
+    baseline = file("$rootDir/config/detekt/baseline.xml")
+    
+    // Parallel-Verarbeitung für schnellere Checks
+    parallel = true
+}

android/app/src/main/java/dev/dettmer/simplenotes/MainActivity.kt

@@ -39,8 +39,11 @@ import kotlinx.coroutines.launch
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.withContext
 import dev.dettmer.simplenotes.sync.WebDavSyncService
+import dev.dettmer.simplenotes.sync.SyncStateManager
 import androidx.core.splashscreen.SplashScreen.Companion.installSplashScreen
 import androidx.swiperefreshlayout.widget.SwipeRefreshLayout
+import android.view.View
+import android.widget.LinearLayout
 
 class MainActivity : AppCompatActivity() {
     
@@ -50,9 +53,16 @@ class MainActivity : AppCompatActivity() {
     private lateinit var toolbar: MaterialToolbar
     private lateinit var swipeRefreshLayout: SwipeRefreshLayout
     
+    // 🔄 v1.3.1: Sync Status Banner
+    private lateinit var syncStatusBanner: LinearLayout
+    private lateinit var syncStatusText: TextView
+    
     private lateinit var adapter: NotesAdapter
     private val storage by lazy { NotesStorage(this) }
     
+    // Menu reference for sync button state
+    private var optionsMenu: Menu? = null
+    
     // Track pending deletions to prevent flicker when notes reload
     private val pendingDeletions = mutableSetOf<String>()
     
@@ -66,6 +76,8 @@ class MainActivity : AppCompatActivity() {
         private const val REQUEST_SETTINGS = 1002
         private const val MIN_AUTO_SYNC_INTERVAL_MS = 60_000L // 1 Minute
         private const val PREF_LAST_AUTO_SYNC_TIME = "last_auto_sync_timestamp"
+        private const val SYNC_COMPLETED_DELAY_MS = 1500L
+        private const val ERROR_DISPLAY_DELAY_MS = 3000L
     }
     
     /**
@@ -97,9 +109,10 @@ class MainActivity : AppCompatActivity() {
         
         setContentView(R.layout.activity_main)
         
-        // File Logging aktivieren wenn eingestellt
-        if (prefs.getBoolean("file_logging_enabled", false)) {
-            Logger.enableFileLogging(this)
+        // Logger initialisieren und File-Logging aktivieren wenn eingestellt
+        Logger.init(this)
+        if (prefs.getBoolean(Constants.KEY_FILE_LOGGING_ENABLED, false)) {
+            Logger.setFileLoggingEnabled(true)
         }
         
         // Alte Sync-Notifications beim App-Start löschen
@@ -116,6 +129,65 @@ class MainActivity : AppCompatActivity() {
         setupFab()
         
         loadNotes()
+        
+        // 🔄 v1.3.1: Observe sync state for UI updates
+        setupSyncStateObserver()
+    }
+    
+    /**
+     * 🔄 v1.3.1: Beobachtet Sync-Status für UI-Feedback
+     */
+    private fun setupSyncStateObserver() {
+        SyncStateManager.syncStatus.observe(this) { status ->
+            when (status.state) {
+                SyncStateManager.SyncState.SYNCING -> {
+                    // Disable sync controls
+                    setSyncControlsEnabled(false)
+                    // 🔄 v1.3.1: Show sync status banner (ersetzt SwipeRefresh-Animation)
+                    syncStatusText.text = getString(R.string.sync_status_syncing)
+                    syncStatusBanner.visibility = View.VISIBLE
+                }
+                SyncStateManager.SyncState.COMPLETED -> {
+                    // Re-enable sync controls
+                    setSyncControlsEnabled(true)
+                    swipeRefreshLayout.isRefreshing = false
+                    // Show completed briefly, then hide
+                    syncStatusText.text = status.message ?: getString(R.string.sync_status_completed)
+                    lifecycleScope.launch {
+                        kotlinx.coroutines.delay(SYNC_COMPLETED_DELAY_MS)
+                        syncStatusBanner.visibility = View.GONE
+                        SyncStateManager.reset()
+                    }
+                }
+                SyncStateManager.SyncState.ERROR -> {
+                    // Re-enable sync controls
+                    setSyncControlsEnabled(true)
+                    swipeRefreshLayout.isRefreshing = false
+                    // Show error briefly, then hide
+                    syncStatusText.text = status.message ?: getString(R.string.sync_status_error)
+                    lifecycleScope.launch {
+                        kotlinx.coroutines.delay(ERROR_DISPLAY_DELAY_MS)
+                        syncStatusBanner.visibility = View.GONE
+                        SyncStateManager.reset()
+                    }
+                }
+                SyncStateManager.SyncState.IDLE -> {
+                    setSyncControlsEnabled(true)
+                    swipeRefreshLayout.isRefreshing = false
+                    syncStatusBanner.visibility = View.GONE
+                }
+            }
+        }
+    }
+    
+    /**
+     * 🔄 v1.3.1: Aktiviert/deaktiviert Sync-Controls (Button + SwipeRefresh)
+     */
+    private fun setSyncControlsEnabled(enabled: Boolean) {
+        // Menu Sync-Button
+        optionsMenu?.findItem(R.id.action_sync)?.isEnabled = enabled
+        // SwipeRefresh
+        swipeRefreshLayout.isEnabled = enabled
     }
     
     override fun onResume() {
@@ -151,6 +223,12 @@ class MainActivity : AppCompatActivity() {
             return
         }
         
+        // 🔄 v1.3.1: Check if sync already running
+        if (!SyncStateManager.tryStartSync("auto-$source")) {
+            Logger.d(TAG, "⏭️ Auto-sync ($source): Another sync already in progress")
+            return
+        }
+        
         Logger.d(TAG, "🔄 Auto-sync triggered ($source)")
         
         // Update last sync timestamp
@@ -163,6 +241,7 @@ class MainActivity : AppCompatActivity() {
                 // 🔥 v1.1.2: Check if there are unsynced changes first (performance optimization)
                 if (!syncService.hasUnsyncedChanges()) {
                     Logger.d(TAG, "⏭️ Auto-sync ($source): No unsynced changes - skipping")
+                    SyncStateManager.reset()
                     return@launch
                 }
                 
@@ -173,6 +252,7 @@ class MainActivity : AppCompatActivity() {
                 
                 if (!isReachable) {
                     Logger.d(TAG, "⏭️ Auto-sync ($source): Server not reachable - skipping silently")
+                    SyncStateManager.reset()
                     return@launch
                 }
                 
@@ -184,6 +264,7 @@ class MainActivity : AppCompatActivity() {
                 // Feedback abhängig von Source
                 if (result.isSuccess && result.syncedCount > 0) {
                     Logger.d(TAG, "✅ Auto-sync successful ($source): ${result.syncedCount} notes")
+                    SyncStateManager.markCompleted("${result.syncedCount} Notizen")
                     
                     // onResume: Nur Success-Toast
                     showToast("✅ Gesynct: ${result.syncedCount} Notizen")
@@ -191,14 +272,17 @@ class MainActivity : AppCompatActivity() {
                     
                 } else if (result.isSuccess) {
                     Logger.d(TAG, "ℹ️ Auto-sync ($source): No changes")
+                    SyncStateManager.markCompleted()
                     
                 } else {
                     Logger.e(TAG, "❌ Auto-sync failed ($source): ${result.errorMessage}")
+                    SyncStateManager.markError(result.errorMessage)
                     // Kein Toast - App ist im Hintergrund
                 }
                 
             } catch (e: Exception) {
                 Logger.e(TAG, "💥 Auto-sync exception ($source): ${e.message}")
+                SyncStateManager.markError(e.message)
                 // Kein Toast - App ist im Hintergrund
             }
         }
@@ -235,6 +319,10 @@ class MainActivity : AppCompatActivity() {
         fabAddNote = findViewById(R.id.fabAddNote)
         toolbar = findViewById(R.id.toolbar)
         swipeRefreshLayout = findViewById<SwipeRefreshLayout>(R.id.swipeRefreshLayout)
+        
+        // 🔄 v1.3.1: Sync Status Banner
+        syncStatusBanner = findViewById(R.id.syncStatusBanner)
+        syncStatusText = findViewById(R.id.syncStatusText)
     }
     
     private fun setupToolbar() {
@@ -262,6 +350,12 @@ class MainActivity : AppCompatActivity() {
         swipeRefreshLayout.setOnRefreshListener {
             Logger.d(TAG, "🔄 Pull-to-Refresh triggered - starting manual sync")
             
+            // 🔄 v1.3.1: Check if sync already running (Banner zeigt Status)
+            if (!SyncStateManager.tryStartSync("pullToRefresh")) {
+                swipeRefreshLayout.isRefreshing = false
+                return@setOnRefreshListener
+            }
+            
             lifecycleScope.launch {
                 try {
                     val prefs = getSharedPreferences(Constants.PREFS_NAME, Context.MODE_PRIVATE)
@@ -269,7 +363,7 @@ class MainActivity : AppCompatActivity() {
                     
                     if (serverUrl.isNullOrEmpty()) {
                         showToast("⚠️ Server noch nicht konfiguriert")
-                        swipeRefreshLayout.isRefreshing = false
+                        SyncStateManager.reset()
                         return@launch
                     }
                     
@@ -278,15 +372,13 @@ class MainActivity : AppCompatActivity() {
                     // 🔥 v1.1.2: Check if there are unsynced changes first (performance optimization)
                     if (!syncService.hasUnsyncedChanges()) {
                         Logger.d(TAG, "⏭️ No unsynced changes, skipping server reachability check")
-                        showToast("✅ Bereits synchronisiert")
-                        swipeRefreshLayout.isRefreshing = false
+                        SyncStateManager.markCompleted("Bereits synchronisiert")
                         return@launch
                     }
                     
                     // Check if server is reachable
                     if (!syncService.isServerReachable()) {
-                        showToast("⚠️ Server nicht erreichbar")
-                        swipeRefreshLayout.isRefreshing = false
+                        SyncStateManager.markError("Server nicht erreichbar")
                         return@launch
                     }
                     
@@ -294,16 +386,14 @@ class MainActivity : AppCompatActivity() {
                     val result = syncService.syncNotes()
                     
                     if (result.isSuccess) {
-                        showToast("✅ ${result.syncedCount} Notizen synchronisiert")
+                        SyncStateManager.markCompleted("${result.syncedCount} Notizen")
                         loadNotes()
                     } else {
-                        showToast("❌ Sync fehlgeschlagen: ${result.errorMessage}")
+                        SyncStateManager.markError(result.errorMessage)
                     }
                 } catch (e: Exception) {
                     Logger.e(TAG, "Pull-to-Refresh sync failed", e)
-                    showToast("❌ Fehler: ${e.message}")
-                } finally {
-                    swipeRefreshLayout.isRefreshing = false
+                    SyncStateManager.markError(e.message)
                 }
             }
         }
@@ -430,16 +520,28 @@ class MainActivity : AppCompatActivity() {
                                     val success = webdavService.deleteNoteFromServer(note.id)
                                     if (success) {
                                         runOnUiThread {
-                                            Toast.makeText(this@MainActivity, "Vom Server gelöscht", Toast.LENGTH_SHORT).show()
+                                            Toast.makeText(
+                                                this@MainActivity,
+                                                "Vom Server gelöscht",
+                                                Toast.LENGTH_SHORT
+                                            ).show()
                                         }
                                     } else {
                                         runOnUiThread {
-                                            Toast.makeText(this@MainActivity, "Server-Löschung fehlgeschlagen", Toast.LENGTH_LONG).show()
+                                            Toast.makeText(
+                                                this@MainActivity,
+                                                "Server-Löschung fehlgeschlagen",
+                                                Toast.LENGTH_LONG
+                                            ).show()
                                         }
                                     }
                                 } catch (e: Exception) {
                                     runOnUiThread {
-                                        Toast.makeText(this@MainActivity, "Server-Fehler: ${e.message}", Toast.LENGTH_LONG).show()
+                                        Toast.makeText(
+                                            this@MainActivity,
+                                            "Server-Fehler: ${e.message}",
+                                            Toast.LENGTH_LONG
+                                        ).show()
                                     }
                                 }
                             }
@@ -493,6 +595,11 @@ class MainActivity : AppCompatActivity() {
     }
     
     private fun triggerManualSync() {
+        // 🔄 v1.3.1: Check if sync already running (Banner zeigt Status)
+        if (!SyncStateManager.tryStartSync("manual")) {
+            return
+        }
+        
         lifecycleScope.launch {
             try {
                 // Create sync service
@@ -501,12 +608,10 @@ class MainActivity : AppCompatActivity() {
                 // 🔥 v1.1.2: Check if there are unsynced changes first (performance optimization)
                 if (!syncService.hasUnsyncedChanges()) {
                     Logger.d(TAG, "⏭️ Manual Sync: No unsynced changes - skipping")
-                    showToast("✅ Bereits synchronisiert")
+                    SyncStateManager.markCompleted("Bereits synchronisiert")
                     return@launch
                 }
                 
-                showToast("Starte Synchronisation...")
-                
                 // ⭐ WICHTIG: Server-Erreichbarkeits-Check VOR Sync (wie in SyncWorker)
                 val isReachable = withContext(Dispatchers.IO) {
                     syncService.isServerReachable()
@@ -514,7 +619,7 @@ class MainActivity : AppCompatActivity() {
                 
                 if (!isReachable) {
                     Logger.d(TAG, "⏭️ Manual Sync: Server not reachable - aborting")
-                    showToast("Server nicht erreichbar")
+                    SyncStateManager.markError("Server nicht erreichbar")
                     return@launch
                 }
                 
@@ -525,20 +630,21 @@ class MainActivity : AppCompatActivity() {
                 
                 // Show result
                 if (result.isSuccess) {
-                    showToast("Sync erfolgreich: ${result.syncedCount} Notizen")
+                    SyncStateManager.markCompleted("${result.syncedCount} Notizen")
                     loadNotes() // Reload notes
                 } else {
-                    showToast("Sync Fehler: ${result.errorMessage}")
+                    SyncStateManager.markError(result.errorMessage)
                 }
                 
             } catch (e: Exception) {
-                showToast("Sync Fehler: ${e.message}")
+                SyncStateManager.markError(e.message)
             }
         }
     }
     
     override fun onCreateOptionsMenu(menu: Menu): Boolean {
         menuInflater.inflate(R.menu.menu_main, menu)
+        optionsMenu = menu  // 🔄 v1.3.1: Store reference for sync button state
         return true
     }
     

android/app/src/main/java/dev/dettmer/simplenotes/SettingsActivity.kt

@@ -25,8 +25,6 @@ import androidx.localbroadcastmanager.content.LocalBroadcastManager
 import com.google.android.material.appbar.MaterialToolbar
 import com.google.android.material.card.MaterialCardView
 import com.google.android.material.color.DynamicColors
-import com.google.android.material.switchmaterial.SwitchMaterial
-import kotlinx.coroutines.CoroutineScope
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.launch
 import dev.dettmer.simplenotes.backup.BackupManager
@@ -34,11 +32,11 @@ import dev.dettmer.simplenotes.backup.RestoreMode
 import dev.dettmer.simplenotes.utils.UrlValidator
 import kotlinx.coroutines.withContext
 import dev.dettmer.simplenotes.sync.WebDavSyncService
+import dev.dettmer.simplenotes.sync.SyncStateManager
 import dev.dettmer.simplenotes.sync.NetworkMonitor
 import dev.dettmer.simplenotes.utils.Constants
 import dev.dettmer.simplenotes.utils.Logger
 import dev.dettmer.simplenotes.utils.showToast
-import java.io.File
 import java.net.HttpURLConnection
 import java.net.URL
 import java.text.SimpleDateFormat
@@ -51,6 +49,7 @@ class SettingsActivity : AppCompatActivity() {
         private const val GITHUB_REPO_URL = "https://github.com/inventory69/simple-notes-sync"
         private const val GITHUB_PROFILE_URL = "https://github.com/inventory69"
         private const val LICENSE_URL = "https://github.com/inventory69/simple-notes-sync/blob/main/LICENSE"
+        private const val CONNECTION_TIMEOUT_MS = 3000
     }
     
     private lateinit var textInputLayoutServerUrl: com.google.android.material.textfield.TextInputLayout
@@ -83,6 +82,11 @@ class SettingsActivity : AppCompatActivity() {
     private lateinit var cardDeveloperProfile: MaterialCardView
     private lateinit var cardLicense: MaterialCardView
     
+    // Debug Section UI
+    private lateinit var switchFileLogging: com.google.android.material.materialswitch.MaterialSwitch
+    private lateinit var buttonExportLogs: Button
+    private lateinit var buttonClearLogs: Button
+    
     // Backup Manager
     private val backupManager by lazy { BackupManager(this) }
     
@@ -124,6 +128,7 @@ class SettingsActivity : AppCompatActivity() {
         setupListeners()
         setupSyncIntervalPicker()
         setupAboutSection()
+        setupDebugSection()
     }
     
     private fun findViews() {
@@ -156,6 +161,11 @@ class SettingsActivity : AppCompatActivity() {
         cardGitHubRepo = findViewById(R.id.cardGitHubRepo)
         cardDeveloperProfile = findViewById(R.id.cardDeveloperProfile)
         cardLicense = findViewById(R.id.cardLicense)
+        
+        // Debug Section UI
+        switchFileLogging = findViewById(R.id.switchFileLogging)
+        buttonExportLogs = findViewById(R.id.buttonExportLogs)
+        buttonClearLogs = findViewById(R.id.buttonClearLogs)
     }
     
     private fun loadSettings() {
@@ -313,7 +323,10 @@ class SettingsActivity : AppCompatActivity() {
      */
     private fun setupSyncIntervalPicker() {
         // Load current interval from preferences
-        val currentInterval = prefs.getLong(Constants.PREF_SYNC_INTERVAL_MINUTES, Constants.DEFAULT_SYNC_INTERVAL_MINUTES)
+        val currentInterval = prefs.getLong(
+            Constants.PREF_SYNC_INTERVAL_MINUTES,
+            Constants.DEFAULT_SYNC_INTERVAL_MINUTES
+        )
         
         // Set checked radio button based on current interval
         val checkedId = when (currentInterval) {
@@ -386,6 +399,109 @@ class SettingsActivity : AppCompatActivity() {
         }
     }
     
+    /**
+     * Setup Debug section with file logging toggle and export functionality
+     */
+    private fun setupDebugSection() {
+        // Load current file logging state
+        val fileLoggingEnabled = prefs.getBoolean(Constants.KEY_FILE_LOGGING_ENABLED, false)
+        switchFileLogging.isChecked = fileLoggingEnabled
+        
+        // Update Logger state
+        Logger.setFileLoggingEnabled(fileLoggingEnabled)
+        
+        // Toggle file logging
+        switchFileLogging.setOnCheckedChangeListener { _, isChecked ->
+            prefs.edit().putBoolean(Constants.KEY_FILE_LOGGING_ENABLED, isChecked).apply()
+            Logger.setFileLoggingEnabled(isChecked)
+            
+            if (isChecked) {
+                showToast("📝 Datei-Logging aktiviert")
+                Logger.i(TAG, "File logging enabled by user")
+            } else {
+                showToast("📝 Datei-Logging deaktiviert")
+            }
+        }
+        
+        // Export logs button
+        buttonExportLogs.setOnClickListener {
+            exportAndShareLogs()
+        }
+        
+        // Clear logs button
+        buttonClearLogs.setOnClickListener {
+            showClearLogsConfirmation()
+        }
+    }
+    
+    /**
+     * Export logs and share via system share sheet
+     */
+    private fun exportAndShareLogs() {
+        lifecycleScope.launch {
+            try {
+                val logFile = Logger.getLogFile(this@SettingsActivity)
+                
+                if (logFile == null || !logFile.exists() || logFile.length() == 0L) {
+                    showToast("📭 Keine Logs vorhanden")
+                    return@launch
+                }
+                
+                // Create share intent using FileProvider
+                val logUri = FileProvider.getUriForFile(
+                    this@SettingsActivity,
+                    "${BuildConfig.APPLICATION_ID}.fileprovider",
+                    logFile
+                )
+                
+                val shareIntent = Intent(Intent.ACTION_SEND).apply {
+                    type = "text/plain"
+                    putExtra(Intent.EXTRA_STREAM, logUri)
+                    putExtra(Intent.EXTRA_SUBJECT, "SimpleNotes Sync Logs")
+                    addFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION)
+                }
+                
+                startActivity(Intent.createChooser(shareIntent, "Logs teilen via..."))
+                Logger.i(TAG, "Logs exported and shared")
+                
+            } catch (e: Exception) {
+                Logger.e(TAG, "Failed to export logs", e)
+                showToast("❌ Fehler beim Exportieren: ${e.message}")
+            }
+        }
+    }
+    
+    /**
+     * Show confirmation dialog before clearing logs
+     */
+    private fun showClearLogsConfirmation() {
+        AlertDialog.Builder(this)
+            .setTitle("Logs löschen?")
+            .setMessage("Alle gespeicherten Sync-Logs werden unwiderruflich gelöscht.")
+            .setPositiveButton("Löschen") { _, _ ->
+                clearLogs()
+            }
+            .setNegativeButton("Abbrechen", null)
+            .show()
+    }
+    
+    /**
+     * Clear all log files
+     */
+    private fun clearLogs() {
+        try {
+            val cleared = Logger.clearLogFile(this)
+            if (cleared) {
+                showToast("🗑️ Logs gelöscht")
+            } else {
+                showToast("📭 Keine Logs zum Löschen")
+            }
+        } catch (e: Exception) {
+            Logger.e(TAG, "Failed to clear logs", e)
+            showToast("❌ Fehler beim Löschen: ${e.message}")
+        }
+    }
+    
     /**
      * Opens URL in browser
      */
@@ -467,6 +583,14 @@ class SettingsActivity : AppCompatActivity() {
     }
     
     private fun syncNow() {
+        // 🔄 v1.3.1: Check if sync already running (Button wird deaktiviert)
+        if (!SyncStateManager.tryStartSync("settings")) {
+            return
+        }
+        
+        // Disable button during sync
+        buttonSyncNow.isEnabled = false
+        
         lifecycleScope.launch {
             try {
                 val syncService = WebDavSyncService(this@SettingsActivity)
@@ -474,14 +598,16 @@ class SettingsActivity : AppCompatActivity() {
                 // 🔥 v1.1.2: Check if there are unsynced changes first (performance optimization)
                 if (!syncService.hasUnsyncedChanges()) {
                     showToast("✅ Bereits synchronisiert")
+                    SyncStateManager.markCompleted()
                     return@launch
                 }
                 
-                showToast("Synchronisiere...")
+                showToast("🔄 Synchronisiere...")
                 
                 // ⭐ WICHTIG: Server-Erreichbarkeits-Check VOR Sync (wie in anderen Triggern)
                 if (!syncService.isServerReachable()) {
                     showToast("⚠️ Server nicht erreichbar")
+                    SyncStateManager.markError("Server nicht erreichbar")
                     checkServerStatus() // Server-Status aktualisieren
                     return@launch
                 }
@@ -490,18 +616,24 @@ class SettingsActivity : AppCompatActivity() {
                 
                 if (result.isSuccess) {
                     if (result.hasConflicts) {
-                        showToast("Sync abgeschlossen. ${result.conflictCount} Konflikte erkannt!")
+                        showToast("✅ Sync abgeschlossen. ${result.conflictCount} Konflikte erkannt!")
                     } else {
-                        showToast("Erfolgreich! ${result.syncedCount} Notizen synchronisiert")
+                        showToast("✅ Erfolgreich! ${result.syncedCount} Notizen synchronisiert")
                     }
+                    SyncStateManager.markCompleted("${result.syncedCount} Notizen")
                     checkServerStatus() // ✅ Server-Status nach Sync aktualisieren
                 } else {
-                    showToast("Sync fehlgeschlagen: ${result.errorMessage}")
+                    showToast("❌ Sync fehlgeschlagen: ${result.errorMessage}")
+                    SyncStateManager.markError(result.errorMessage)
                     checkServerStatus() // ✅ Auch bei Fehler aktualisieren
                 }
             } catch (e: Exception) {
-                showToast("Fehler: ${e.message}")
+                showToast("❌ Fehler: ${e.message}")
+                SyncStateManager.markError(e.message)
                 checkServerStatus() // ✅ Auch bei Exception aktualisieren
+            } finally {
+                // Re-enable button
+                buttonSyncNow.isEnabled = true
             }
         }
     }
@@ -523,8 +655,8 @@ class SettingsActivity : AppCompatActivity() {
                 try {
                     val url = URL(serverUrl)
                     val connection = url.openConnection() as HttpURLConnection
-                    connection.connectTimeout = 3000
-                    connection.readTimeout = 3000
+                    connection.connectTimeout = CONNECTION_TIMEOUT_MS
+                    connection.readTimeout = CONNECTION_TIMEOUT_MS
                     val code = connection.responseCode
                     connection.disconnect()
                     code in 200..299 || code == 401  // 401 = Server da, Auth fehlt
@@ -633,7 +765,10 @@ class SettingsActivity : AppCompatActivity() {
                             .apply()
                         
                         updateMarkdownButtonVisibility()
-                        showToast("Markdown Auto-Sync aktiviert - Notizen werden als .md-Dateien exportiert und importiert")
+                        showToast(
+                            "Markdown Auto-Sync aktiviert - " +
+                                "Notizen werden als .md-Dateien exportiert und importiert"
+                        )
                     }
                     
                 } catch (e: Exception) {
@@ -687,11 +822,13 @@ class SettingsActivity : AppCompatActivity() {
             intent.data = Uri.parse("package:$packageName")
             startActivity(intent)
         } catch (e: Exception) {
+            Logger.w(TAG, "Failed to open battery optimization settings: ${e.message}")
             // Fallback: Open general battery settings
             try {
                 val intent = Intent(Settings.ACTION_IGNORE_BATTERY_OPTIMIZATION_SETTINGS)
                 startActivity(intent)
             } catch (e2: Exception) {
+                Logger.w(TAG, "Failed to open fallback battery settings: ${e2.message}")
                 showToast("Bitte Akku-Optimierung manuell deaktivieren")
             }
         }
@@ -710,49 +847,6 @@ class SettingsActivity : AppCompatActivity() {
         }
     }
     
-    private fun showRestoreConfirmation() {
-        android.app.AlertDialog.Builder(this)
-            .setTitle(R.string.restore_confirmation_title)
-            .setMessage(R.string.restore_confirmation_message)
-            .setPositiveButton(R.string.restore_button) { _, _ ->
-                performRestore()
-            }
-            .setNegativeButton(R.string.cancel, null)
-            .show()
-    }
-    
-    private fun performRestore() {
-        val progressDialog = android.app.ProgressDialog(this).apply {
-            setMessage(getString(R.string.restore_progress))
-            setCancelable(false)
-            show()
-        }
-        
-        CoroutineScope(Dispatchers.Main).launch {
-            try {
-                val webdavService = WebDavSyncService(this@SettingsActivity)
-                val result = withContext(Dispatchers.IO) {
-                    webdavService.restoreFromServer()
-                }
-                
-                progressDialog.dismiss()
-                
-                if (result.isSuccess) {
-                    showToast(getString(R.string.restore_success, result.restoredCount))
-                    // Refresh MainActivity's note list
-                    setResult(RESULT_OK)
-                } else {
-                    showToast(getString(R.string.restore_error, result.errorMessage))
-                }
-                checkServerStatus()
-            } catch (e: Exception) {
-                progressDialog.dismiss()
-                showToast(getString(R.string.restore_error, e.message))
-                checkServerStatus()
-            }
-        }
-    }
-    
     override fun onOptionsItemSelected(item: MenuItem): Boolean {
         return when (item.itemId) {
             android.R.id.home -> {
@@ -815,7 +909,6 @@ class SettingsActivity : AppCompatActivity() {
         }
         
         // Custom View mit Radio Buttons
-        val dialogView = layoutInflater.inflate(android.R.layout.select_dialog_singlechoice, null)
         val radioGroup = android.widget.RadioGroup(this).apply {
             orientation = android.widget.RadioGroup.VERTICAL
             setPadding(50, 20, 50, 20)
@@ -824,20 +917,20 @@ class SettingsActivity : AppCompatActivity() {
         // Radio Buttons erstellen
         val radioMerge = android.widget.RadioButton(this).apply {
             text = "⚪ Zusammenführen (Standard)\n   → Neue hinzufügen, Bestehende behalten"
-            id = 0
+            id = android.view.View.generateViewId()
             isChecked = true
             setPadding(10, 10, 10, 10)
         }
         
         val radioReplace = android.widget.RadioButton(this).apply {
             text = "⚪ Ersetzen\n   → Alle löschen & Backup importieren"
-            id = 1
+            id = android.view.View.generateViewId()
             setPadding(10, 10, 10, 10)
         }
         
         val radioOverwrite = android.widget.RadioButton(this).apply {
             text = "⚪ Duplikate überschreiben\n   → Backup gewinnt bei Konflikten"
-            id = 2
+            id = android.view.View.generateViewId()
             setPadding(10, 10, 10, 10)
         }
         
@@ -876,8 +969,8 @@ class SettingsActivity : AppCompatActivity() {
             .setView(mainLayout)
             .setPositiveButton("Wiederherstellen") { _, _ ->
                 val selectedMode = when (radioGroup.checkedRadioButtonId) {
-                    1 -> RestoreMode.REPLACE
-                    2 -> RestoreMode.OVERWRITE_DUPLICATES
+                    radioReplace.id -> RestoreMode.REPLACE
+                    radioOverwrite.id -> RestoreMode.OVERWRITE_DUPLICATES
                     else -> RestoreMode.MERGE
                 }
                 
@@ -908,12 +1001,12 @@ class SettingsActivity : AppCompatActivity() {
                 progressDialog.dismiss()
                 
                 if (result.success) {
-                    val message = result.message ?: "Wiederhergestellt: ${result.imported_notes} Notizen"
+                    val message = result.message ?: "Wiederhergestellt: ${result.importedNotes} Notizen"
                     showToast("✅ $message")
                     
                     // Refresh MainActivity's note list
                     setResult(RESULT_OK)
-                    broadcastNotesChanged(result.imported_notes)
+                    broadcastNotesChanged(result.importedNotes)
                 } else {
                     showErrorDialog("Wiederherstellung fehlgeschlagen", result.error ?: "Unbekannter Fehler")
                 }
@@ -1022,10 +1115,16 @@ class SettingsActivity : AppCompatActivity() {
                 progressDialog.dismiss()
                 
                 // Erfolgs-Nachricht
-                val message = "✅ Sync abgeschlossen\n📤 ${result.exportedCount} exportiert\n📥 ${result.importedCount} importiert"
+                val message = "✅ Sync abgeschlossen\n" +
+                    "📤 ${result.exportedCount} exportiert\n" +
+                    "📥 ${result.importedCount} importiert"
                 showToast(message)
                 
-                Logger.d("SettingsActivity", "Manual markdown sync: exported=${result.exportedCount}, imported=${result.importedCount}")
+                Logger.d(
+                    "SettingsActivity",
+                    "Manual markdown sync: exported=${result.exportedCount}, " +
+                        "imported=${result.importedCount}"
+                )
                 
             } catch (e: Exception) {
                 progressDialog?.dismiss()

android/app/src/main/java/dev/dettmer/simplenotes/backup/BackupManager.kt

@@ -49,10 +49,10 @@ class BackupManager(private val context: Context) {
             Logger.d(TAG, "   Found ${allNotes.size} notes to backup")
             
             val backupData = BackupData(
-                backup_version = BACKUP_VERSION,
-                created_at = System.currentTimeMillis(),
-                notes_count = allNotes.size,
-                app_version = BuildConfig.VERSION_NAME,
+                backupVersion = BACKUP_VERSION,
+                createdAt = System.currentTimeMillis(),
+                notesCount = allNotes.size,
+                appVersion = BuildConfig.VERSION_NAME,
                 notes = allNotes
             )
             
@@ -65,7 +65,7 @@ class BackupManager(private val context: Context) {
             
             BackupResult(
                 success = true,
-                notes_count = allNotes.size,
+                notesCount = allNotes.size,
                 message = "Backup erstellt: ${allNotes.size} Notizen"
             )
             
@@ -99,10 +99,10 @@ class BackupManager(private val context: Context) {
             
             val allNotes = storage.loadAllNotes()
             val backupData = BackupData(
-                backup_version = BACKUP_VERSION,
-                created_at = System.currentTimeMillis(),
-                notes_count = allNotes.size,
-                app_version = BuildConfig.VERSION_NAME,
+                backupVersion = BACKUP_VERSION,
+                createdAt = System.currentTimeMillis(),
+                notesCount = allNotes.size,
+                appVersion = BuildConfig.VERSION_NAME,
                 notes = allNotes
             )
             
@@ -149,7 +149,7 @@ class BackupManager(private val context: Context) {
             }
             
             val backupData = gson.fromJson(jsonString, BackupData::class.java)
-            Logger.d(TAG, "   Backup valid: ${backupData.notes_count} notes, version ${backupData.backup_version}")
+            Logger.d(TAG, "   Backup valid: ${backupData.notesCount} notes, version ${backupData.backupVersion}")
             
             // 3. Auto-Backup erstellen (Sicherheitsnetz)
             val autoBackupUri = createAutoBackup()
@@ -164,7 +164,7 @@ class BackupManager(private val context: Context) {
                 RestoreMode.OVERWRITE_DUPLICATES -> restoreOverwriteDuplicates(backupData.notes)
             }
             
-            Logger.d(TAG, "✅ Restore completed: ${result.imported_notes} imported, ${result.skipped_notes} skipped")
+            Logger.d(TAG, "✅ Restore completed: ${result.importedNotes} imported, ${result.skippedNotes} skipped")
             result
             
         } catch (e: Exception) {
@@ -184,10 +184,11 @@ class BackupManager(private val context: Context) {
             val backupData = gson.fromJson(jsonString, BackupData::class.java)
             
             // Version kompatibel?
-            if (backupData.backup_version > BACKUP_VERSION) {
+            if (backupData.backupVersion > BACKUP_VERSION) {
                 return ValidationResult(
                     isValid = false,
-                    errorMessage = "Backup-Version nicht unterstützt (v${backupData.backup_version} benötigt v${BACKUP_VERSION}+)"
+                    errorMessage = "Backup-Version nicht unterstützt " +
+                        "(v${backupData.backupVersion} benötigt v${BACKUP_VERSION}+)"
                 )
             }
             
@@ -238,8 +239,8 @@ class BackupManager(private val context: Context) {
         
         return RestoreResult(
             success = true,
-            imported_notes = newNotes.size,
-            skipped_notes = skippedNotes,
+            importedNotes = newNotes.size,
+            skippedNotes = skippedNotes,
             message = "${newNotes.size} neue Notizen importiert, $skippedNotes übersprungen"
         )
     }
@@ -259,8 +260,8 @@ class BackupManager(private val context: Context) {
         
         return RestoreResult(
             success = true,
-            imported_notes = backupNotes.size,
-            skipped_notes = 0,
+            importedNotes = backupNotes.size,
+            skippedNotes = 0,
             message = "Alle Notizen ersetzt: ${backupNotes.size} importiert"
         )
     }
@@ -283,9 +284,9 @@ class BackupManager(private val context: Context) {
         
         return RestoreResult(
             success = true,
-            imported_notes = newNotes.size,
-            skipped_notes = 0,
-            overwritten_notes = overwrittenNotes.size,
+            importedNotes = newNotes.size,
+            skippedNotes = 0,
+            overwrittenNotes = overwrittenNotes.size,
             message = "${newNotes.size} neu, ${overwrittenNotes.size} überschrieben"
         )
     }
@@ -312,12 +313,17 @@ class BackupManager(private val context: Context) {
 
 /**
  * Backup-Daten Struktur (JSON)
+ * NOTE: Property names use @SerializedName for JSON compatibility with snake_case
  */
 data class BackupData(
-    val backup_version: Int,
-    val created_at: Long,
-    val notes_count: Int,
-    val app_version: String,
+    @com.google.gson.annotations.SerializedName("backup_version")
+    val backupVersion: Int,
+    @com.google.gson.annotations.SerializedName("created_at")
+    val createdAt: Long,
+    @com.google.gson.annotations.SerializedName("notes_count")
+    val notesCount: Int,
+    @com.google.gson.annotations.SerializedName("app_version")
+    val appVersion: String,
     val notes: List<Note>
 )
 
@@ -335,7 +341,7 @@ enum class RestoreMode {
  */
 data class BackupResult(
     val success: Boolean,
-    val notes_count: Int = 0,
+    val notesCount: Int = 0,
     val message: String? = null,
     val error: String? = null
 )
@@ -345,9 +351,9 @@ data class BackupResult(
  */
 data class RestoreResult(
     val success: Boolean,
-    val imported_notes: Int = 0,
-    val skipped_notes: Int = 0,
-    val overwritten_notes: Int = 0,
+    val importedNotes: Int = 0,
+    val skippedNotes: Int = 0,
+    val overwrittenNotes: Int = 0,
     val message: String? = null,
     val error: String? = null
 )

android/app/src/main/java/dev/dettmer/simplenotes/models/DeletionTracker.kt

@@ -1,5 +1,6 @@
 package dev.dettmer.simplenotes.models
 
+import dev.dettmer.simplenotes.utils.Logger
 import org.json.JSONArray
 import org.json.JSONObject
 
@@ -49,6 +50,8 @@ data class DeletionTracker(
     }
     
     companion object {
+        private const val TAG = "DeletionTracker"
+        
         fun fromJson(json: String): DeletionTracker? {
             return try {
                 val jsonObject = JSONObject(json)
@@ -70,6 +73,7 @@ data class DeletionTracker(
                 
                 DeletionTracker(version, deletedNotes)
             } catch (e: Exception) {
+                Logger.w(TAG, "Failed to parse DeletionTracker JSON: ${e.message}")
                 null
             }
         }

android/app/src/main/java/dev/dettmer/simplenotes/models/Note.kt

@@ -1,5 +1,6 @@
 package dev.dettmer.simplenotes.models
 
+import dev.dettmer.simplenotes.utils.Logger
 import java.text.SimpleDateFormat
 import java.util.Date
 import java.util.Locale
@@ -49,11 +50,14 @@ $content
     }
     
     companion object {
+        private const val TAG = "Note"
+        
         fun fromJson(json: String): Note? {
             return try {
                 val gson = com.google.gson.Gson()
                 gson.fromJson(json, Note::class.java)
             } catch (e: Exception) {
+                Logger.w(TAG, "Failed to parse JSON: ${e.message}")
                 null
             }
         }
@@ -102,6 +106,7 @@ $content
                     syncStatus = SyncStatus.SYNCED  // Annahme: Vom Server importiert
                 )
             } catch (e: Exception) {
+                Logger.w(TAG, "Failed to parse Markdown: ${e.message}")
                 null
             }
         }
@@ -126,6 +131,7 @@ $content
                 sdf.timeZone = TimeZone.getTimeZone("UTC")
                 sdf.parse(dateString)?.time ?: System.currentTimeMillis()
             } catch (e: Exception) {
+                Logger.w(TAG, "Failed to parse ISO8601 date '$dateString': ${e.message}")
                 System.currentTimeMillis()  // Fallback
             }
         }

android/app/src/main/java/dev/dettmer/simplenotes/sync/NetworkMonitor.kt

@@ -227,7 +227,11 @@ class NetworkMonitor(private val context: Context) {
             if (isWifi) {
                 lastConnectedNetworkId = activeNetwork.toString()
                 Logger.d(TAG, "    ✅ Initial WiFi network: $lastConnectedNetworkId")
-                Logger.d(TAG, "    📡 WiFi already connected at startup - onAvailable() will only trigger on network change")
+                Logger.d(
+                    TAG,
+                    "    📡 WiFi already connected at startup - " +
+                        "onAvailable() will only trigger on network change"
+                )
             } else {
                 lastConnectedNetworkId = null
                 Logger.d(TAG, "    ⚠️ Not on WiFi at startup")
@@ -268,7 +272,7 @@ class NetworkMonitor(private val context: Context) {
             connectivityManager.unregisterNetworkCallback(networkCallback)
             Logger.d(TAG, "✅ WiFi monitoring stopped")
         } catch (e: Exception) {
-            // Already unregistered
+            Logger.w(TAG, "NetworkCallback already unregistered: ${e.message}")
         }
     }
 }

android/app/src/main/java/dev/dettmer/simplenotes/sync/SyncStateManager.kt

@@ -0,0 +1,129 @@
+package dev.dettmer.simplenotes.sync
+
+import androidx.lifecycle.LiveData
+import androidx.lifecycle.MutableLiveData
+import dev.dettmer.simplenotes.utils.Logger
+
+/**
+ * 🔄 v1.3.1: Zentrale Verwaltung des Sync-Status
+ * 
+ * Verhindert doppelte Syncs und informiert die UI über den aktuellen Status.
+ * Thread-safe Singleton mit LiveData für UI-Reaktivität.
+ */
+object SyncStateManager {
+    
+    private const val TAG = "SyncStateManager"
+    
+    /**
+     * Mögliche Sync-Zustände
+     */
+    enum class SyncState {
+        IDLE,           // Kein Sync aktiv
+        SYNCING,        // Sync läuft gerade
+        COMPLETED,      // Sync erfolgreich abgeschlossen (kurz anzeigen)
+        ERROR           // Sync fehlgeschlagen (kurz anzeigen)
+    }
+    
+    /**
+     * Detaillierte Sync-Informationen für UI
+     */
+    data class SyncStatus(
+        val state: SyncState = SyncState.IDLE,
+        val message: String? = null,
+        val source: String? = null,  // "manual", "auto", "pullToRefresh", "background"
+        val timestamp: Long = System.currentTimeMillis()
+    )
+    
+    // Private mutable LiveData
+    private val _syncStatus = MutableLiveData(SyncStatus())
+    
+    // Public immutable LiveData für Observer
+    val syncStatus: LiveData<SyncStatus> = _syncStatus
+    
+    // Lock für Thread-Sicherheit
+    private val lock = Any()
+    
+    /**
+     * Prüft ob gerade ein Sync läuft
+     */
+    val isSyncing: Boolean
+        get() = _syncStatus.value?.state == SyncState.SYNCING
+    
+    /**
+     * Versucht einen Sync zu starten.
+     * @return true wenn Sync gestartet werden kann, false wenn bereits einer läuft
+     */
+    fun tryStartSync(source: String): Boolean {
+        synchronized(lock) {
+            if (isSyncing) {
+                Logger.d(TAG, "⚠️ Sync already in progress, rejecting new sync from: $source")
+                return false
+            }
+            
+            Logger.d(TAG, "🔄 Starting sync from: $source")
+            _syncStatus.postValue(
+                SyncStatus(
+                    state = SyncState.SYNCING,
+                    message = "Synchronisiere...",
+                    source = source
+                )
+            )
+            return true
+        }
+    }
+    
+    /**
+     * Markiert Sync als erfolgreich abgeschlossen
+     */
+    fun markCompleted(message: String? = null) {
+        synchronized(lock) {
+            val currentSource = _syncStatus.value?.source
+            Logger.d(TAG, "✅ Sync completed from: $currentSource")
+            _syncStatus.postValue(
+                SyncStatus(
+                    state = SyncState.COMPLETED,
+                    message = message,
+                    source = currentSource
+                )
+            )
+        }
+    }
+    
+    /**
+     * Markiert Sync als fehlgeschlagen
+     */
+    fun markError(errorMessage: String?) {
+        synchronized(lock) {
+            val currentSource = _syncStatus.value?.source
+            Logger.e(TAG, "❌ Sync failed from: $currentSource - $errorMessage")
+            _syncStatus.postValue(
+                SyncStatus(
+                    state = SyncState.ERROR,
+                    message = errorMessage,
+                    source = currentSource
+                )
+            )
+        }
+    }
+    
+    /**
+     * Setzt Status zurück auf IDLE
+     */
+    fun reset() {
+        synchronized(lock) {
+            _syncStatus.postValue(SyncStatus())
+        }
+    }
+    
+    /**
+     * Aktualisiert die Nachricht während des Syncs (z.B. Progress)
+     */
+    fun updateMessage(message: String) {
+        synchronized(lock) {
+            val current = _syncStatus.value ?: return
+            if (current.state == SyncState.SYNCING) {
+                _syncStatus.postValue(current.copy(message = message))
+            }
+        }
+    }
+}

android/app/src/main/java/dev/dettmer/simplenotes/sync/SyncWorker.kt

@@ -117,7 +117,11 @@ class SyncWorker(
             
             if (BuildConfig.DEBUG) {
                 Logger.d(TAG, "📍 Step 4: Processing result")
-                Logger.d(TAG, "📦 Sync result: success=${result.isSuccess}, count=${result.syncedCount}, error=${result.errorMessage}")
+                Logger.d(
+                    TAG,
+                    "📦 Sync result: success=${result.isSuccess}, " +
+                        "count=${result.syncedCount}, error=${result.errorMessage}"
+                )
             }
             
             if (result.isSuccess) {

android/app/src/main/java/dev/dettmer/simplenotes/sync/WebDavSyncService.kt

@@ -12,14 +12,15 @@ import dev.dettmer.simplenotes.models.SyncStatus
 import dev.dettmer.simplenotes.storage.NotesStorage
 import dev.dettmer.simplenotes.utils.Constants
 import dev.dettmer.simplenotes.utils.Logger
+import dev.dettmer.simplenotes.utils.SyncException
 import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.sync.Mutex
 import kotlinx.coroutines.withContext
 import okhttp3.OkHttpClient
 import java.net.Inet4Address
 import java.net.InetAddress
 import java.net.InetSocketAddress
 import java.net.NetworkInterface
-import java.net.Proxy
 import java.net.Socket
 import java.net.URL
 import java.util.Date
@@ -37,11 +38,23 @@ class WebDavSyncService(private val context: Context) {
     
     companion object {
         private const val TAG = "WebDavSyncService"
+        private const val SOCKET_TIMEOUT_MS = 2000
+        private const val MAX_FILENAME_LENGTH = 200
+        private const val ETAG_PREVIEW_LENGTH = 8
+        
+        // 🔒 v1.3.1: Mutex um parallele Syncs zu verhindern
+        private val syncMutex = Mutex()
     }
     
     private val storage: NotesStorage
     private val prefs = context.getSharedPreferences(Constants.PREFS_NAME, Context.MODE_PRIVATE)
     private var markdownDirEnsured = false  // Cache für Ordner-Existenz
+    private var notesDirEnsured = false     // ⚡ v1.3.1: Cache für /notes/ Ordner-Existenz
+    
+    // ⚡ v1.3.1 Performance: Session-Caches (werden am Ende von syncNotes() geleert)
+    private var sessionSardine: Sardine? = null
+    private var sessionWifiAddress: InetAddress? = null
+    private var sessionWifiAddressChecked = false  // Flag ob WiFi-Check bereits durchgeführt
     
     init {
         if (BuildConfig.DEBUG) {
@@ -73,10 +86,26 @@ class WebDavSyncService(private val context: Context) {
         }
     }
     
+    /**
+     * ⚡ v1.3.1: Gecachte WiFi-Adresse zurückgeben oder berechnen
+     */
+    private fun getOrCacheWiFiAddress(): InetAddress? {
+        // Return cached if already checked this session
+        if (sessionWifiAddressChecked) {
+            return sessionWifiAddress
+        }
+        
+        // Calculate and cache
+        sessionWifiAddress = getWiFiInetAddressInternal()
+        sessionWifiAddressChecked = true
+        return sessionWifiAddress
+    }
+    
     /**
      * Findet WiFi Interface IP-Adresse (um VPN zu umgehen)
      */
-    private fun getWiFiInetAddress(): InetAddress? {
+    @Suppress("ReturnCount") // Early returns for network validation checks
+    private fun getWiFiInetAddressInternal(): InetAddress? {
         try {
             Logger.d(TAG, "🔍 getWiFiInetAddress() called")
             
@@ -120,7 +149,11 @@ class WebDavSyncService(private val context: Context) {
                 while (addresses.hasMoreElements()) {
                     val addr = addresses.nextElement()
                     
-                    Logger.d(TAG, "        Address: ${addr.hostAddress}, IPv4=${addr is Inet4Address}, loopback=${addr.isLoopbackAddress}, linkLocal=${addr.isLinkLocalAddress}")
+                    Logger.d(
+                        TAG,
+                        "        Address: ${addr.hostAddress}, IPv4=${addr is Inet4Address}, " +
+                            "loopback=${addr.isLoopbackAddress}, linkLocal=${addr.isLinkLocalAddress}"
+                    )
                     
                     // Nur IPv4, nicht loopback, nicht link-local
                     if (addr is Inet4Address && !addr.isLoopbackAddress && !addr.isLinkLocalAddress) {
@@ -171,15 +204,35 @@ class WebDavSyncService(private val context: Context) {
         }
     }
     
-    private fun getSardine(): Sardine? {
+    /**
+     * ⚡ v1.3.1: Gecachten Sardine-Client zurückgeben oder erstellen
+     * Spart ~100ms pro Aufruf durch Wiederverwendung
+     */
+    private fun getOrCreateSardine(): Sardine? {
+        // Return cached if available
+        sessionSardine?.let { 
+            Logger.d(TAG, "⚡ Reusing cached Sardine client")
+            return it 
+        }
+        
+        // Create new client
+        val sardine = createSardineClient()
+        sessionSardine = sardine
+        return sardine
+    }
+    
+    /**
+     * Erstellt einen neuen Sardine-Client (intern)
+     */
+    private fun createSardineClient(): Sardine? {
         val username = prefs.getString(Constants.KEY_USERNAME, null) ?: return null
         val password = prefs.getString(Constants.KEY_PASSWORD, null) ?: return null
         
         Logger.d(TAG, "🔧 Creating OkHttpSardine with WiFi binding")
         Logger.d(TAG, "    Context: ${context.javaClass.simpleName}")
         
-        // Versuche WiFi-IP zu finden
-        val wifiAddress = getWiFiInetAddress()
+        // ⚡ v1.3.1: Verwende gecachte WiFi-Adresse
+        val wifiAddress = getOrCacheWiFiAddress()
         
         val okHttpClient = if (wifiAddress != null) {
             Logger.d(TAG, "✅ Using WiFi-bound socket factory")
@@ -196,6 +249,18 @@ class WebDavSyncService(private val context: Context) {
         }
     }
     
+    /**
+     * ⚡ v1.3.1: Session-Caches leeren (am Ende von syncNotes)
+     */
+    private fun clearSessionCache() {
+        sessionSardine = null
+        sessionWifiAddress = null
+        sessionWifiAddressChecked = false
+        notesDirEnsured = false
+        markdownDirEnsured = false
+        Logger.d(TAG, "🧹 Session caches cleared")
+    }
+    
     private fun getServerUrl(): String? {
         return prefs.getString(Constants.KEY_SERVER_URL, null)
     }
@@ -266,6 +331,31 @@ class WebDavSyncService(private val context: Context) {
         }
     }
     
+    /**
+     * ⚡ v1.3.1: Stellt sicher dass notes/ Ordner existiert (mit Cache)
+     * 
+     * Spart ~500ms pro Sync durch Caching
+     */
+    private fun ensureNotesDirectoryExists(sardine: Sardine, notesUrl: String) {
+        if (notesDirEnsured) {
+            Logger.d(TAG, "⚡ notes/ directory already verified (cached)")
+            return
+        }
+        
+        try {
+            Logger.d(TAG, "🔍 Checking if notes/ directory exists...")
+            if (!sardine.exists(notesUrl)) {
+                Logger.d(TAG, "📁 Creating notes/ directory...")
+                sardine.createDirectory(notesUrl)
+            }
+            Logger.d(TAG, "    ✅ notes/ directory ready")
+            notesDirEnsured = true
+        } catch (e: Exception) {
+            Logger.e(TAG, "💥 CRASH checking/creating notes/ directory!", e)
+            throw e
+        }
+    }
+    
     /**
      * Checks if server has changes using E-Tag caching
      * 
@@ -280,6 +370,7 @@ class WebDavSyncService(private val context: Context) {
      * 3. If changed → server has updates
      * 4. If unchanged → skip sync
      */
+    @Suppress("ReturnCount") // Early returns for conditional checks
     private suspend fun checkServerForChanges(sardine: Sardine, serverUrl: String): Boolean {
         return try {
             val startTime = System.currentTimeMillis()
@@ -298,47 +389,13 @@ class WebDavSyncService(private val context: Context) {
             
             // ====== JSON FILES CHECK (/notes/) ======
             
-            // Optimierung 1: E-Tag Check (fastest - ~100ms)
-            val cachedETag = prefs.getString("notes_collection_etag", null)
-            var jsonHasChanges = false
+            // ⚡ v1.3.1: File-level E-Tag check in downloadRemoteNotes() is optimal!
+            // Collection E-Tag doesn't work (server-dependent, doesn't track file changes)
+            // → Always proceed to download phase where file-level E-Tags provide fast skips
             
-            if (cachedETag != null) {
-                try {
-                    val resources = sardine.list(notesUrl, 0)  // Depth 0 = only collection itself
-                    val currentETag = resources.firstOrNull()?.contentLength?.toString() ?: ""
-                    
-                    if (currentETag == cachedETag) {
-                        val elapsed = System.currentTimeMillis() - startTime
-                        Logger.d(TAG, "⚡ E-Tag match - no JSON changes (${elapsed}ms)")
-                        // Don't return yet - check Markdown too!
-                    } else {
-                        Logger.d(TAG, "🔄 E-Tag changed - JSON files have updates")
-                        return true  // Early return if JSON changed
-                    }
-                } catch (e: Exception) {
-                    Logger.w(TAG, "E-Tag check failed: ${e.message}, falling back to timestamp check")
-                    jsonHasChanges = true
-                }
-            } else {
-                jsonHasChanges = true
-            }
-            
-            // Optimierung 2: Smart Timestamp Check for JSON (medium - ~300ms)
-            if (jsonHasChanges || cachedETag == null) {
-                val resources = sardine.list(notesUrl, 1)  // Depth 1 = collection + children
-                
-                val jsonHasNewer = resources.any { resource ->
-                    !resource.isDirectory && 
-                    resource.name.endsWith(".json") &&
-                    resource.modified?.time?.let { it > lastSyncTime } ?: false
-                }
-                
-                if (jsonHasNewer) {
-                    val elapsed = System.currentTimeMillis() - startTime
-                    Logger.d(TAG, "🔍 JSON check: hasNewer=true (${resources.size} resources, ${elapsed}ms)")
-                    return true
-                }
-            }
+            // For hasUnsyncedChanges(): Conservative approach - assume changes may exist
+            // Actual file-level E-Tag checks in downloadRemoteNotes() will skip unchanged files (0ms each)
+            var hasJsonChanges = true  // Assume yes, let file E-Tags optimize
             
             // ====== MARKDOWN FILES CHECK (/notes-md/) ======
             // IMPORTANT: E-Tag for collections does NOT work for content changes!
@@ -365,7 +422,11 @@ class WebDavSyncService(private val context: Context) {
                         resource.modified?.time?.let { 
                             val hasNewer = it > lastSyncTime
                             if (hasNewer) {
-                                Logger.d(TAG, "   📄 ${resource.name}: modified=${resource.modified}, lastSync=$lastSyncTime")
+                                Logger.d(
+                                    TAG,
+                                    "   📄 ${resource.name}: modified=${resource.modified}, " +
+                                        "lastSync=$lastSyncTime"
+                                )
                             }
                             hasNewer
                         } ?: false
@@ -382,7 +443,15 @@ class WebDavSyncService(private val context: Context) {
             }
             
             val elapsed = System.currentTimeMillis() - startTime
-            Logger.d(TAG, "✅ No changes detected (JSON + Markdown checked, ${elapsed}ms)")
+            
+            // Return TRUE if JSON or Markdown have potential changes
+            // (File-level E-Tags will do the actual skip optimization during sync)
+            if (hasJsonChanges) {
+                Logger.d(TAG, "✅ JSON may have changes - will check file E-Tags (${elapsed}ms)")
+                return true
+            }
+            
+            Logger.d(TAG, "✅ No changes detected (Markdown checked, ${elapsed}ms)")
             return false
             
         } catch (e: Exception) {
@@ -429,7 +498,7 @@ class WebDavSyncService(private val context: Context) {
             }
             
             // Perform intelligent server check
-            val sardine = getSardine()
+            val sardine = getOrCreateSardine()
             val serverUrl = getServerUrl()
             
             if (sardine == null || serverUrl == null) {
@@ -468,10 +537,10 @@ class WebDavSyncService(private val context: Context) {
             
             Logger.d(TAG, "🔍 Checking server reachability: $host:$port")
             
-            // Socket-Check mit 2s Timeout
+            // Socket-Check mit Timeout
             // Gibt dem Netzwerk Zeit für Initialisierung (DHCP, Routing, Gateway)
             val socket = Socket()
-            socket.connect(InetSocketAddress(host, port), 2000)
+            socket.connect(InetSocketAddress(host, port), SOCKET_TIMEOUT_MS)
             socket.close()
             
             Logger.d(TAG, "✅ Server is reachable")
@@ -484,7 +553,7 @@ class WebDavSyncService(private val context: Context) {
     
     suspend fun testConnection(): SyncResult = withContext(Dispatchers.IO) {
         return@withContext try {
-            val sardine = getSardine() ?: return@withContext SyncResult(
+            val sardine = getOrCreateSardine() ?: return@withContext SyncResult(
                 isSuccess = false,
                 errorMessage = "Server-Zugangsdaten nicht konfiguriert"
             )
@@ -529,6 +598,17 @@ class WebDavSyncService(private val context: Context) {
     }
     
     suspend fun syncNotes(): SyncResult = withContext(Dispatchers.IO) {
+        // 🔒 v1.3.1: Verhindere parallele Syncs
+        if (!syncMutex.tryLock()) {
+            Logger.d(TAG, "⏭️ Sync already in progress - skipping")
+            return@withContext SyncResult(
+                isSuccess = true,
+                syncedCount = 0,
+                errorMessage = null
+            )
+        }
+        
+        try {
             Logger.d(TAG, "═══════════════════════════════════════")
             Logger.d(TAG, "🔄 syncNotes() ENTRY")
             Logger.d(TAG, "Context: ${context.javaClass.simpleName}")
@@ -538,9 +618,9 @@ class WebDavSyncService(private val context: Context) {
             Logger.d(TAG, "📍 Step 1: Getting Sardine client")
             
             val sardine = try {
-                getSardine()
+                getOrCreateSardine()
             } catch (e: Exception) {
-                Logger.e(TAG, "💥 CRASH in getSardine()!", e)
+                Logger.e(TAG, "💥 CRASH in getOrCreateSardine()!", e)
                 e.printStackTrace()
                 throw e
             }
@@ -571,20 +651,9 @@ class WebDavSyncService(private val context: Context) {
             var conflictCount = 0
             
             Logger.d(TAG, "📍 Step 3: Checking server directory")
-            // Ensure notes/ directory exists
+            // ⚡ v1.3.1: Verwende gecachte Directory-Checks
             val notesUrl = getNotesUrl(serverUrl)
-            try {
-                Logger.d(TAG, "🔍 Checking if notes/ directory exists...")
-                if (!sardine.exists(notesUrl)) {
-                    Logger.d(TAG, "📁 Creating notes/ directory...")
-                    sardine.createDirectory(notesUrl)
-                }
-                Logger.d(TAG, "    ✅ notes/ directory ready")
-            } catch (e: Exception) {
-                Logger.e(TAG, "💥 CRASH checking/creating notes/ directory!", e)
-                e.printStackTrace()
-                throw e
-            }
+            ensureNotesDirectoryExists(sardine, notesUrl)
             
             // Ensure notes-md/ directory exists (for Markdown export)
             ensureMarkdownDirectoryExists(sardine, serverUrl)
@@ -613,7 +682,11 @@ class WebDavSyncService(private val context: Context) {
                 )
                 syncedCount += downloadResult.downloadedCount
                 conflictCount += downloadResult.conflictCount
-                Logger.d(TAG, "✅ Downloaded: ${downloadResult.downloadedCount} notes, Conflicts: ${downloadResult.conflictCount}")
+                Logger.d(
+                    TAG,
+                    "✅ Downloaded: ${downloadResult.downloadedCount} notes, " +
+                        "Conflicts: ${downloadResult.conflictCount}"
+                )
             } catch (e: Exception) {
                 Logger.e(TAG, "💥 CRASH in downloadRemoteNotes()!", e)
                 e.printStackTrace()
@@ -697,6 +770,12 @@ class WebDavSyncService(private val context: Context) {
                 }
             )
         }
+        } finally {
+            // ⚡ v1.3.1: Session-Caches leeren
+            clearSessionCache()
+            // 🔒 v1.3.1: Sync-Mutex freigeben
+            syncMutex.unlock()
+        }
     }
     
     private fun uploadLocalNotes(sardine: Sardine, serverUrl: String): Int {
@@ -712,13 +791,33 @@ class WebDavSyncService(private val context: Context) {
                     val noteUrl = "$notesUrl${note.id}.json"
                     val jsonBytes = note.toJson().toByteArray()
                     
+                    Logger.d(TAG, "   📤 Uploading: ${note.id}.json (${note.title})")
                     sardine.put(noteUrl, jsonBytes, "application/json")
+                    Logger.d(TAG, "      ✅ Upload successful")
                     
                     // Update sync status
                     val updatedNote = note.copy(syncStatus = SyncStatus.SYNCED)
                     storage.saveNote(updatedNote)
                     uploadedCount++
                     
+                    // ⚡ v1.3.1: Refresh E-Tag after upload to prevent re-download
+                    // Get new E-Tag from server via PROPFIND
+                    try {
+                        val uploadedResource = sardine.list(noteUrl, 0).firstOrNull()
+                        val newETag = uploadedResource?.etag
+                        if (newETag != null) {
+                            prefs.edit().putString("etag_json_${note.id}", newETag).apply()
+                            Logger.d(TAG, "      ⚡ Cached new E-Tag: ${newETag.take(ETAG_PREVIEW_LENGTH)}")
+                        } else {
+                            // Fallback: invalidate if server doesn't provide E-Tag
+                            prefs.edit().remove("etag_json_${note.id}").apply()
+                            Logger.d(TAG, "      ⚠️ No E-Tag from server, invalidated cache")
+                        }
+                    } catch (e: Exception) {
+                        Logger.w(TAG, "      ⚠️ Failed to refresh E-Tag: ${e.message}")
+                        prefs.edit().remove("etag_json_${note.id}").apply()
+                    }
+                    
                     // 2. Markdown-Export (NEU in v1.2.0)
                     // Läuft NACH erfolgreichem JSON-Upload
                     if (markdownExportEnabled) {
@@ -732,6 +831,7 @@ class WebDavSyncService(private val context: Context) {
                     }
                 }
             } catch (e: Exception) {
+                Logger.w(TAG, "Upload failed for note ${note.id}, marking as pending: ${e.message}")
                 // Mark as pending for retry
                 val updatedNote = note.copy(syncStatus = SyncStatus.PENDING)
                 storage.saveNote(updatedNote)
@@ -780,7 +880,7 @@ class WebDavSyncService(private val context: Context) {
         return title
             .replace(Regex("[<>:\"/\\\\|?*]"), "_")  // Ersetze verbotene Zeichen
             .replace(Regex("\\s+"), " ")              // Normalisiere Whitespace
-            .take(200)                                 // Max 200 Zeichen (Reserve für .md)
+            .take(MAX_FILENAME_LENGTH)                 // Max Zeichen (Reserve für .md)
             .trim('_', ' ')                            // Trim Underscores/Spaces
     }
     
@@ -800,8 +900,8 @@ class WebDavSyncService(private val context: Context) {
     ): Int = withContext(Dispatchers.IO) {
         Logger.d(TAG, "🔄 Starting initial Markdown export for all notes...")
         
-        // Erstelle Sardine-Client mit gegebenen Credentials
-        val wifiAddress = getWiFiInetAddress()
+        // ⚡ v1.3.1: Use cached WiFi address
+        val wifiAddress = getOrCacheWiFiAddress()
         
         val okHttpClient = if (wifiAddress != null) {
             Logger.d(TAG, "✅ Using WiFi-bound socket factory")
@@ -854,6 +954,15 @@ class WebDavSyncService(private val context: Context) {
         }
         
         Logger.d(TAG, "✅ Initial export completed: $exportedCount/$totalCount notes")
+        
+        // ⚡ v1.3.1: Set lastSyncTimestamp to enable timestamp-based skip on next sync
+        // This prevents re-downloading all MD files on the first manual sync after initial export
+        if (exportedCount > 0) {
+            val timestamp = System.currentTimeMillis()
+            prefs.edit().putLong("last_sync_timestamp", timestamp).apply()
+            Logger.d(TAG, "💾 Set lastSyncTimestamp after initial export (enables fast next sync)")
+        }
+        
         return@withContext exportedCount
     }
     
@@ -886,17 +995,66 @@ class WebDavSyncService(private val context: Context) {
             val notesUrl = getNotesUrl(serverUrl)
             Logger.d(TAG, "🔍 Phase 1: Checking /notes/ at: $notesUrl")
             
+            // ⚡ v1.3.1: Performance - Get last sync time for skip optimization
+            val lastSyncTime = getLastSyncTimestamp()
+            var skippedUnchanged = 0
+            
             if (sardine.exists(notesUrl)) {
                 Logger.d(TAG, "   ✅ /notes/ exists, scanning...")
                 val resources = sardine.list(notesUrl)
+                val jsonFiles = resources.filter { !it.isDirectory && it.name.endsWith(".json") }
+                Logger.d(TAG, "   📊 Found ${jsonFiles.size} JSON files on server")
                 
-                for (resource in resources) {
-                    if (resource.isDirectory || !resource.name.endsWith(".json")) {
+                for (resource in jsonFiles) {
+                    
+                    val noteId = resource.name.removeSuffix(".json")
+                    val noteUrl = notesUrl.trimEnd('/') + "/" + resource.name
+                    
+                    // ⚡ v1.3.1: HYBRID PERFORMANCE - Timestamp + E-Tag (like Markdown!)
+                    val serverETag = resource.etag
+                    val cachedETag = prefs.getString("etag_json_$noteId", null)
+                    val serverModified = resource.modified?.time ?: 0L
+                    
+                    // 🐛 DEBUG: Log every file check to diagnose performance
+                    val serverETagPreview = serverETag?.take(ETAG_PREVIEW_LENGTH) ?: "null"
+                    val cachedETagPreview = cachedETag?.take(ETAG_PREVIEW_LENGTH) ?: "null"
+                    Logger.d(
+                        TAG,
+                        "   🔍 [$noteId] etag=$serverETagPreview/$cachedETagPreview " +
+                            "modified=$serverModified lastSync=$lastSyncTime"
+                    )
+                    
+                    // PRIMARY: Timestamp check (works on first sync!)
+                    // Same logic as Markdown sync - skip if not modified since last sync
+                    if (!forceOverwrite && lastSyncTime > 0 && serverModified <= lastSyncTime) {
+                        skippedUnchanged++
+                        Logger.d(TAG, "   ⏭️ Skipping $noteId: Not modified since last sync (timestamp)")
+                        processedIds.add(noteId)
                         continue
                     }
                     
-                    // 🔧 Fix: Build full URL instead of using href directly
-                    val noteUrl = notesUrl.trimEnd('/') + "/" + resource.name
+                    // SECONDARY: E-Tag check (for performance after first sync)
+                    // Catches cases where file was re-uploaded with same content
+                    if (!forceOverwrite && serverETag != null && serverETag == cachedETag) {
+                        skippedUnchanged++
+                        Logger.d(TAG, "   ⏭️ Skipping $noteId: E-Tag match (content unchanged)")
+                        processedIds.add(noteId)
+                        continue
+                    }
+                    
+                    // 🐛 DEBUG: Log download reason
+                    val downloadReason = when {
+                        lastSyncTime == 0L -> "First sync ever"
+                        serverModified > lastSyncTime && serverETag == null -> "Modified + no server E-Tag"
+                        serverModified > lastSyncTime && cachedETag == null -> "Modified + no cached E-Tag"
+                        serverModified > lastSyncTime -> "Modified + E-Tag changed"
+                        serverETag == null -> "No server E-Tag"
+                        cachedETag == null -> "No cached E-Tag"
+                        else -> "E-Tag changed"
+                    }
+                    Logger.d(TAG, "   📥 Downloading $noteId: $downloadReason")
+                    
+                    // Download and process
                     val jsonContent = sardine.get(noteUrl).bufferedReader().use { it.readText() }
                     val remoteNote = Note.fromJson(jsonContent) ?: continue
                     
@@ -928,12 +1086,22 @@ class WebDavSyncService(private val context: Context) {
                             storage.saveNote(remoteNote.copy(syncStatus = SyncStatus.SYNCED))
                             downloadedCount++
                             Logger.d(TAG, "   ✅ Downloaded from /notes/: ${remoteNote.id}")
+                            
+                            // ⚡ Cache E-Tag for next sync
+                            if (serverETag != null) {
+                                prefs.edit().putString("etag_json_$noteId", serverETag).apply()
+                            }
                         }
                         forceOverwrite -> {
                             // OVERWRITE mode: Always replace regardless of timestamps
                             storage.saveNote(remoteNote.copy(syncStatus = SyncStatus.SYNCED))
                             downloadedCount++
                             Logger.d(TAG, "   ♻️ Overwritten from /notes/: ${remoteNote.id}")
+                            
+                            // ⚡ Cache E-Tag for next sync
+                            if (serverETag != null) {
+                                prefs.edit().putString("etag_json_$noteId", serverETag).apply()
+                            }
                         }
                         localNote.updatedAt < remoteNote.updatedAt -> {
                             // Remote is newer
@@ -946,11 +1114,20 @@ class WebDavSyncService(private val context: Context) {
                                 storage.saveNote(remoteNote.copy(syncStatus = SyncStatus.SYNCED))
                                 downloadedCount++
                                 Logger.d(TAG, "   ✅ Updated from /notes/: ${remoteNote.id}")
+                                
+                                // ⚡ Cache E-Tag for next sync
+                                if (serverETag != null) {
+                                    prefs.edit().putString("etag_json_$noteId", serverETag).apply()
                                 }
                             }
                         }
                     }
-                Logger.d(TAG, "   📊 Phase 1: $downloadedCount downloaded, $skippedDeleted skipped (deleted)")
+                }
+                Logger.d(
+                    TAG,
+                    "   📊 Phase 1: $downloadedCount downloaded, $skippedDeleted skipped (deleted), " +
+                        "$skippedUnchanged skipped (unchanged)"
+                )
             } else {
                 Logger.w(TAG, "   ⚠️ /notes/ does not exist, skipping Phase 1")
             }
@@ -1065,36 +1242,14 @@ class WebDavSyncService(private val context: Context) {
     private fun saveLastSyncTimestamp() {
         val now = System.currentTimeMillis()
         
-        // v1.3.0: Save E-Tag only for JSON (Markdown uses timestamp check)
-        try {
-            val sardine = getSardine()
-            val serverUrl = getServerUrl()
-            
-            if (sardine != null && serverUrl != null) {
-                val notesUrl = getNotesUrl(serverUrl)
-                
-                // JSON E-Tag only
-                val notesResources = sardine.list(notesUrl, 0)
-                val notesETag = notesResources.firstOrNull()?.contentLength?.toString()
-                
+        // ⚡ v1.3.1: Simplified - file-level E-Tags cached individually in downloadRemoteNotes()
+        // No need for collection E-Tag (doesn't work reliably across WebDAV servers)
         prefs.edit()
             .putLong(Constants.KEY_LAST_SYNC, now)
             .putLong(Constants.KEY_LAST_SUCCESSFUL_SYNC, now)
-                    .putString("notes_collection_etag", notesETag)
             .apply()
         
-                Logger.d(TAG, "💾 Saved sync timestamp + JSON E-Tag")
-                return
-            }
-        } catch (e: Exception) {
-            Logger.w(TAG, "Failed to save E-Tag: ${e.message}")
-        }
-        
-        // Fallback: Save timestamp only
-        prefs.edit()
-            .putLong(Constants.KEY_LAST_SYNC, now)
-            .putLong(Constants.KEY_LAST_SUCCESSFUL_SYNC, now)  // 🔥 v1.1.2: Track successful sync
-            .apply()
+        Logger.d(TAG, "💾 Saved sync timestamp (file E-Tags cached individually)")
     }
     
     fun getLastSyncTimestamp(): Long {
@@ -1114,7 +1269,7 @@ class WebDavSyncService(private val context: Context) {
         mode: dev.dettmer.simplenotes.backup.RestoreMode = dev.dettmer.simplenotes.backup.RestoreMode.REPLACE
     ): RestoreResult = withContext(Dispatchers.IO) {
         return@withContext try {
-            val sardine = getSardine() ?: return@withContext RestoreResult(
+            val sardine = getOrCreateSardine() ?: return@withContext RestoreResult(
                 isSuccess = false,
                 errorMessage = "Server-Zugangsdaten nicht konfiguriert",
                 restoredCount = 0
@@ -1137,6 +1292,20 @@ class WebDavSyncService(private val context: Context) {
             Logger.d(TAG, "🗑️ Clearing deletion tracker (restore mode)")
             storage.clearDeletionTracker()
             
+            // ⚡ v1.3.1 FIX: Clear lastSyncTimestamp to force download ALL files
+            // Restore = "Server ist die Quelle" → Ignore lokale Sync-History
+            val previousSyncTime = getLastSyncTimestamp()
+            prefs.edit().putLong("last_sync_timestamp", 0).apply()
+            Logger.d(TAG, "🔄 Cleared lastSyncTimestamp (was: $previousSyncTime) - will download all files")
+            
+            // ⚡ v1.3.1 FIX: Clear E-Tag caches to force re-download
+            val editor = prefs.edit()
+            prefs.all.keys.filter { it.startsWith("etag_json_") }.forEach { key ->
+                editor.remove(key)
+            }
+            editor.apply()
+            Logger.d(TAG, "🔄 Cleared E-Tag caches - will re-download all files")
+            
             // Determine forceOverwrite flag
             val forceOverwrite = (mode == dev.dettmer.simplenotes.backup.RestoreMode.OVERWRITE_DUPLICATES)
             Logger.d(TAG, "forceOverwrite: $forceOverwrite")
@@ -1163,7 +1332,11 @@ class WebDavSyncService(private val context: Context) {
             
             // 🆕 v1.2.2: Use downloadRemoteNotes() with Root fallback + forceOverwrite
             // 🆕 v1.3.0: Pass FRESH empty tracker to avoid loading stale cached data
-            Logger.d(TAG, "📡 Calling downloadRemoteNotes() - includeRootFallback: true, forceOverwrite: $forceOverwrite")
+            Logger.d(
+                TAG,
+                "📡 Calling downloadRemoteNotes() - " +
+                    "includeRootFallback: true, forceOverwrite: $forceOverwrite"
+            )
             val emptyTracker = DeletionTracker()  // Fresh empty tracker after clear
             val result = downloadRemoteNotes(
                 sardine = sardine, 
@@ -1314,6 +1487,8 @@ class WebDavSyncService(private val context: Context) {
     /**
      * Auto-import Markdown files during regular sync (v1.3.0)
      * Called automatically if KEY_MARKDOWN_AUTO_IMPORT is enabled
+     * 
+     * ⚡ v1.3.1: Performance-Optimierung - Skip unveränderte Dateien
      */
     private fun importMarkdownFiles(sardine: Sardine, serverUrl: String): Int {
         return try {
@@ -1329,11 +1504,26 @@ class WebDavSyncService(private val context: Context) {
             
             val mdResources = sardine.list(mdUrl).filter { !it.isDirectory && it.name.endsWith(".md") }
             var importedCount = 0
+            var skippedCount = 0  // ⚡ v1.3.1: Zähle übersprungene Dateien
             
             Logger.d(TAG, "   📂 Found ${mdResources.size} markdown files")
             
+            // ⚡ v1.3.1: Performance-Optimierung - Letzten Sync-Zeitpunkt holen
+            val lastSyncTime = getLastSyncTimestamp()
+            Logger.d(TAG, "   📅 Last sync: ${Date(lastSyncTime)}")
+            
             for (resource in mdResources) {
                 try {
+                    val serverModifiedTime = resource.modified?.time ?: 0L
+                    
+                    // ⚡ v1.3.1: PERFORMANCE - Skip wenn Datei seit letztem Sync nicht geändert wurde
+                    // Das ist der Haupt-Performance-Fix! Spart ~500ms pro Datei bei Nextcloud.
+                    if (lastSyncTime > 0 && serverModifiedTime <= lastSyncTime) {
+                        skippedCount++
+                        Logger.d(TAG, "   ⏭️ Skipping ${resource.name}: not modified since last sync")
+                        continue
+                    }
+                    
                     Logger.d(TAG, "   🔍 Processing: ${resource.name}, modified=${resource.modified}")
                     
                     // Build full URL
@@ -1349,16 +1539,43 @@ class WebDavSyncService(private val context: Context) {
                         Logger.w(TAG, "      ⚠️ Failed to parse ${resource.name} - fromMarkdown returned null")
                         continue
                     }
-                    Logger.d(TAG, "      Parsed: id=${mdNote.id}, title=${mdNote.title}, updatedAt=${Date(mdNote.updatedAt)}")
+                    Logger.d(
+                        TAG,
+                        "      Parsed: id=${mdNote.id}, title=${mdNote.title}, " +
+                            "updatedAt=${Date(mdNote.updatedAt)}"
+                    )
                     
                     val localNote = storage.loadNote(mdNote.id)
-                    Logger.d(TAG, "      Local note: ${if (localNote == null) "NOT FOUND" else "exists, updatedAt=${Date(localNote.updatedAt)}, syncStatus=${localNote.syncStatus}"}")
+                    Logger.d(
+                        TAG,
+                        "      Local note: " + if (localNote == null) {
+                            "NOT FOUND"
+                        } else {
+                            "exists, updatedAt=${Date(localNote.updatedAt)}, " +
+                                "syncStatus=${localNote.syncStatus}"
+                        }
+                    )
                     
-                    // Use server file modification time for reliable change detection
-                    val serverModifiedTime = resource.modified?.time ?: 0L
-                    Logger.d(TAG, "      Comparison: serverModified=$serverModifiedTime, localUpdated=${localNote?.updatedAt ?: 0L}")
+                    // ⚡ v1.3.1: Content-basierte Erkennung
+                    // Wichtig: Vergleiche IMMER den Inhalt, wenn die Datei seit letztem Sync geändert wurde!
+                    // Der YAML-Timestamp kann veraltet sein (z.B. bei externer Bearbeitung ohne Obsidian)
+                    Logger.d(
+                        TAG,
+                        "      Comparison: mdUpdatedAt=${mdNote.updatedAt}, " +
+                            "localUpdated=${localNote?.updatedAt ?: 0L}"
+                    )
                     
-                    // Conflict resolution: Last-Write-Wins
+                    // Content-Vergleich: Ist der Inhalt tatsächlich unterschiedlich?
+                    val contentChanged = localNote != null && (
+                        mdNote.content != localNote.content || 
+                        mdNote.title != localNote.title
+                    )
+                    
+                    if (contentChanged) {
+                        Logger.d(TAG, "      📝 Content differs from local!")
+                    }
+                    
+                    // Conflict resolution: Content-First, dann Timestamp
                     when {
                         localNote == null -> {
                             // New note from desktop
@@ -1366,57 +1583,51 @@ class WebDavSyncService(private val context: Context) {
                             importedCount++
                             Logger.d(TAG, "   ✅ Imported new from Markdown: ${mdNote.title}")
                         }
-                        serverModifiedTime > localNote.updatedAt -> {
-                            // Server file is newer (based on modification time)
-                            Logger.d(TAG, "      Decision: Server is newer!")
+                        // ⚡ v1.3.1 FIX: Content-basierter Skip - nur wenn Inhalt UND Timestamp gleich
+                        localNote.syncStatus == SyncStatus.SYNCED &&
+                            !contentChanged &&
+                            localNote.updatedAt >= mdNote.updatedAt -> {
+                            // Inhalt identisch UND Timestamps passen → Skip
+                            skippedCount++
+                            Logger.d(
+                                TAG,
+                                "   ⏭️ Skipped ${mdNote.title}: content identical " +
+                                    "(local=${localNote.updatedAt}, md=${mdNote.updatedAt})"
+                            )
+                        }
+                        // ⚡ v1.3.1 FIX: Content geändert aber YAML-Timestamp nicht aktualisiert → Importieren!
+                        contentChanged && localNote.syncStatus == SyncStatus.SYNCED -> {
+                            // Inhalt wurde extern geändert ohne YAML-Update → mit aktuellem Timestamp importieren
+                            val newTimestamp = System.currentTimeMillis()
+                            storage.saveNote(mdNote.copy(
+                                updatedAt = newTimestamp,
+                                syncStatus = SyncStatus.SYNCED
+                            ))
+                            importedCount++
+                            Logger.d(TAG, "   ✅ Imported changed content (YAML timestamp outdated): ${mdNote.title}")
+                        }
+                        mdNote.updatedAt > localNote.updatedAt -> {
+                            // Markdown has newer YAML timestamp
+                            Logger.d(TAG, "      Decision: Markdown has newer timestamp!")
                             if (localNote.syncStatus == SyncStatus.PENDING) {
                                 // Conflict: local has pending changes
                                 storage.saveNote(localNote.copy(syncStatus = SyncStatus.CONFLICT))
                                 Logger.w(TAG, "   ⚠️ Conflict: Markdown vs local pending: ${mdNote.id}")
                             } else {
-                                // Content comparison to preserve timestamps on export-only updates
-                                val contentChanged = mdNote.content != localNote.content || 
-                                                   mdNote.title != localNote.title
-                                
-                                // Detect if YAML timestamp wasn't updated despite content change
-                                val yamlInconsistent = contentChanged && mdNote.updatedAt <= localNote.updatedAt
-                                
-                                // Log inconsistencies for debugging
-                                if (yamlInconsistent) {
-                                    Logger.w(TAG, "   ⚠️ Inconsistency: ${mdNote.title}")
-                                    Logger.w(TAG, "      Content changed but YAML timestamp not updated")
-                                    Logger.w(TAG, "      YAML: ${mdNote.updatedAt}, Local: ${localNote.updatedAt}")
-                                    Logger.w(TAG, "      Using current time as fallback")
-                                }
-                                
-                                // Determine final timestamp with auto-correction
-                                val finalUpdatedAt: Long = when {
-                                    // No content change → preserve local timestamp (export-only)
-                                    !contentChanged -> localNote.updatedAt
-                                    
-                                    // Content changed + YAML timestamp properly updated
-                                    !yamlInconsistent -> mdNote.updatedAt
-                                    
-                                    // Content changed + YAML timestamp NOT updated → use current time
-                                    else -> System.currentTimeMillis()
-                                }
-                                
-                                storage.saveNote(mdNote.copy(
-                                    updatedAt = finalUpdatedAt,
-                                    syncStatus = SyncStatus.SYNCED
-                                ))
+                                // Import with the newer YAML timestamp
+                                storage.saveNote(mdNote.copy(syncStatus = SyncStatus.SYNCED))
                                 importedCount++
-                                
-                                // Detailed logging
-                                when {
-                                    !contentChanged -> Logger.d(TAG, "   ✅ Re-synced (export-only, timestamp preserved): ${mdNote.title}")
-                                    yamlInconsistent -> Logger.d(TAG, "   ✅ Updated (content changed, timestamp corrected): ${mdNote.title}")
-                                    else -> Logger.d(TAG, "   ✅ Updated (content changed, YAML timestamp valid): ${mdNote.title}")
-                                }
+                                Logger.d(TAG, "   ✅ Updated from Markdown (newer timestamp): ${mdNote.title}")
                             }
                         }
                         else -> {
-                            Logger.d(TAG, "   ⏭️ Skipped ${mdNote.title}: local is newer (server=$serverModifiedTime, local=${localNote.updatedAt})")
+                            // Local has pending changes but MD is older - keep local
+                            skippedCount++
+                            Logger.d(
+                                TAG,
+                                "   ⏭️ Skipped ${mdNote.title}: local is newer or pending " +
+                                    "(local=${localNote.updatedAt}, md=${mdNote.updatedAt})"
+                            )
                         }
                     }
                 } catch (e: Exception) {
@@ -1425,7 +1636,8 @@ class WebDavSyncService(private val context: Context) {
                 }
             }
             
-            Logger.d(TAG, "   📊 Markdown import complete: $importedCount notes")
+            // ⚡ v1.3.1: Verbessertes Logging mit Skip-Count
+            Logger.d(TAG, "   📊 Markdown import complete: $importedCount imported, $skippedCount skipped (unchanged)")
             importedCount
             
         } catch (e: Exception) {
@@ -1493,7 +1705,7 @@ class WebDavSyncService(private val context: Context) {
      */
     suspend fun deleteNoteFromServer(noteId: String): Boolean = withContext(Dispatchers.IO) {
         return@withContext try {
-            val sardine = getSardine() ?: return@withContext false
+            val sardine = getOrCreateSardine() ?: return@withContext false
             val serverUrl = getServerUrl() ?: return@withContext false
             
             var deletedJson = false
@@ -1563,14 +1775,16 @@ class WebDavSyncService(private val context: Context) {
      */
     suspend fun manualMarkdownSync(): ManualMarkdownSyncResult = withContext(Dispatchers.IO) {
         return@withContext try {
-            val sardine = getSardine() ?: throw Exception("Sardine client konnte nicht erstellt werden")
-            val serverUrl = getServerUrl() ?: throw Exception("Server-URL nicht konfiguriert")
+            val sardine = getOrCreateSardine()
+                ?: throw SyncException("Sardine client konnte nicht erstellt werden")
+            val serverUrl = getServerUrl()
+                ?: throw SyncException("Server-URL nicht konfiguriert")
             
             val username = prefs.getString(Constants.KEY_USERNAME, "") ?: ""
             val password = prefs.getString(Constants.KEY_PASSWORD, "") ?: ""
             
             if (serverUrl.isBlank() || username.isBlank() || password.isBlank()) {
-                throw Exception("WebDAV-Server nicht vollständig konfiguriert")
+                throw SyncException("WebDAV-Server nicht vollständig konfiguriert")
             }
             
             Logger.d(TAG, "🔄 Manual Markdown Sync START")

android/app/src/main/java/dev/dettmer/simplenotes/sync/WifiSyncReceiver.kt

@@ -28,6 +28,7 @@ class WifiSyncReceiver : BroadcastReceiver() {
         }
     }
     
+    @Suppress("ReturnCount") // Early returns for WiFi validation checks
     private fun isConnectedToHomeWifi(context: Context): Boolean {
         val prefs = context.getSharedPreferences(Constants.PREFS_NAME, Context.MODE_PRIVATE)
         val homeSSID = prefs.getString(Constants.KEY_HOME_SSID, null) ?: return false

android/app/src/main/java/dev/dettmer/simplenotes/utils/Constants.kt

@@ -27,6 +27,9 @@ object Constants {
     const val KEY_ALWAYS_CHECK_SERVER = "always_check_server"
     const val KEY_ALWAYS_DELETE_FROM_SERVER = "always_delete_from_server"
     
+    // 🔥 v1.3.1: Debug & Logging
+    const val KEY_FILE_LOGGING_ENABLED = "file_logging_enabled"
+    
     // WorkManager
     const val SYNC_WORK_TAG = "notes_sync"
     const val SYNC_DELAY_SECONDS = 5L

android/app/src/main/java/dev/dettmer/simplenotes/utils/Extensions.kt

@@ -7,6 +7,9 @@ import java.util.Date
 import java.util.Locale
 import java.util.concurrent.TimeUnit
 
+private const val DAYS_THRESHOLD = 7L
+private const val TRUNCATE_SUFFIX_LENGTH = 3
+
 // Toast Extensions
 fun Context.showToast(message: String, duration: Int = Toast.LENGTH_SHORT) {
     Toast.makeText(this, message, duration).show()
@@ -27,7 +30,7 @@ fun Long.toReadableTime(): String {
             val hours = TimeUnit.MILLISECONDS.toHours(diff)
             "Vor $hours Std"
         }
-        diff < TimeUnit.DAYS.toMillis(7) -> {
+        diff < TimeUnit.DAYS.toMillis(DAYS_THRESHOLD) -> {
             val days = TimeUnit.MILLISECONDS.toDays(diff)
             "Vor $days Tagen"
         }
@@ -41,7 +44,7 @@ fun Long.toReadableTime(): String {
 // Truncate long strings
 fun String.truncate(maxLength: Int): String {
     return if (length > maxLength) {
-        substring(0, maxLength - 3) + "..."
+        substring(0, maxLength - TRUNCATE_SUFFIX_LENGTH) + "..."
     } else {
         this
     }

android/app/src/main/java/dev/dettmer/simplenotes/utils/Logger.kt

@@ -5,7 +5,6 @@ import android.util.Log
 import dev.dettmer.simplenotes.BuildConfig
 import java.io.File
 import java.io.FileWriter
-import java.io.PrintWriter
 import java.text.SimpleDateFormat
 import java.util.*
 
@@ -15,10 +14,34 @@ import java.util.*
  */
 object Logger {
     
+    private const val MAX_LOG_ENTRIES = 500 // Nur letzte 500 Einträge
+    
     private var fileLoggingEnabled = false
     private var logFile: File? = null
+    private var appContext: Context? = null
     private val dateFormat = SimpleDateFormat("yyyy-MM-dd HH:mm:ss.SSS", Locale.getDefault())
-    private val maxLogEntries = 500 // Nur letzte 500 Einträge
+    
+    /**
+     * Setzt den File-Logging Status (für UI Toggle)
+     */
+    fun setFileLoggingEnabled(enabled: Boolean) {
+        fileLoggingEnabled = enabled
+        if (!enabled) {
+            logFile = null
+        }
+    }
+    
+    /**
+     * Gibt zurück, ob File-Logging aktiviert ist
+     */
+    fun isFileLoggingEnabled(): Boolean = fileLoggingEnabled
+    
+    /**
+     * Initialisiert den Logger mit App-Context
+     */
+    fun init(context: Context) {
+        appContext = context.applicationContext
+    }
     
     /**
      * Aktiviert File-Logging für Debugging
@@ -50,11 +73,47 @@ object Logger {
      */
     fun getLogFile(): File? = logFile
     
+    /**
+     * Gibt Log-Datei mit Context zurück (für SettingsActivity)
+     */
+    fun getLogFile(context: Context): File? {
+        if (logFile == null && fileLoggingEnabled) {
+            logFile = File(context.filesDir, "simplenotes_debug.log")
+        }
+        return logFile
+    }
+    
+    /**
+     * Löscht die Log-Datei
+     */
+    fun clearLogFile(context: Context): Boolean {
+        return try {
+            val file = File(context.filesDir, "simplenotes_debug.log")
+            if (file.exists()) {
+                file.delete()
+                logFile = null
+                true
+            } else {
+                false
+            }
+        } catch (e: Exception) {
+            Log.e("Logger", "Failed to clear log file", e)
+            false
+        }
+    }
+    
     /**
      * Schreibt Log-Eintrag in Datei
      */
     private fun writeToFile(level: String, tag: String, message: String, throwable: Throwable? = null) {
-        if (!fileLoggingEnabled || logFile == null) return
+        if (!fileLoggingEnabled) return
+        
+        // Lazy-init logFile mit appContext
+        if (logFile == null && appContext != null) {
+            logFile = File(appContext!!.filesDir, "simplenotes_debug.log")
+        }
+        
+        if (logFile == null) return
         
         try {
             val timestamp = dateFormat.format(Date())
@@ -80,13 +139,13 @@ object Logger {
     }
     
     /**
-     * Begrenzt Log-Datei auf maxLogEntries
+     * Begrenzt Log-Datei auf MAX_LOG_ENTRIES
      */
     private fun trimLogFile() {
         try {
             val lines = logFile?.readLines() ?: return
-            if (lines.size > maxLogEntries) {
-                val trimmed = lines.takeLast(maxLogEntries)
+            if (lines.size > MAX_LOG_ENTRIES) {
+                val trimmed = lines.takeLast(MAX_LOG_ENTRIES)
                 logFile?.writeText(trimmed.joinToString("\n") + "\n")
             }
         } catch (e: Exception) {

android/app/src/main/java/dev/dettmer/simplenotes/utils/NotificationHelper.kt

@@ -20,6 +20,7 @@ object NotificationHelper {
     private const val CHANNEL_DESCRIPTION = "Benachrichtigungen über Sync-Status"
     private const val NOTIFICATION_ID = 1001
     private const val SYNC_NOTIFICATION_ID = 2
+    private const val AUTO_CANCEL_TIMEOUT_MS = 30_000L
     
     /**
      * Erstellt Notification Channel (Android 8.0+)
@@ -286,7 +287,7 @@ object NotificationHelper {
         Handler(Looper.getMainLooper()).postDelayed({
             manager.cancel(SYNC_NOTIFICATION_ID)
             Logger.d(TAG, "🗑️ Auto-cancelled error notification after 30s timeout")
-        }, 30_000)
+        }, AUTO_CANCEL_TIMEOUT_MS)
     }
     
     /**

android/app/src/main/java/dev/dettmer/simplenotes/utils/SyncException.kt

@@ -0,0 +1,21 @@
+package dev.dettmer.simplenotes.utils
+
+/**
+ * Exception für Sync-spezifische Fehler
+ * 
+ * Verwendet anstelle von generischen Exceptions für bessere
+ * Fehlerbehandlung und klarere Fehlermeldungen.
+ */
+class SyncException(
+    message: String,
+    cause: Throwable? = null
+) : Exception(message, cause)
+
+/**
+ * Exception für Validierungsfehler
+ * 
+ * Verwendet für ungültige Eingaben oder Konfigurationsfehler.
+ */
+class ValidationException(
+    message: String
+) : IllegalArgumentException(message)

android/app/src/main/java/dev/dettmer/simplenotes/utils/UrlValidator.kt

@@ -8,6 +8,16 @@ import java.net.URL
  */
 object UrlValidator {
     
+    // RFC 1918 Private IP Ranges
+    private const val PRIVATE_CLASS_A_FIRST_OCTET = 10
+    private const val PRIVATE_CLASS_B_FIRST_OCTET = 172
+    private const val PRIVATE_CLASS_B_SECOND_OCTET_MIN = 16
+    private const val PRIVATE_CLASS_B_SECOND_OCTET_MAX = 31
+    private const val PRIVATE_CLASS_C_FIRST_OCTET = 192
+    private const val PRIVATE_CLASS_C_SECOND_OCTET = 168
+    private const val LOCALHOST_FIRST_OCTET = 127
+    private const val OCTET_MAX_VALUE = 255
+    
     /**
      * Prüft ob eine URL eine lokale/private Adresse ist
      * Erlaubt:
@@ -17,6 +27,7 @@ object UrlValidator {
      * - 127.x.x.x (Localhost)
      * - .local domains (mDNS/Bonjour)
      */
+    @Suppress("ReturnCount") // Early returns for validation checks are clearer
     fun isLocalUrl(url: String): Boolean {
         return try {
             val parsedUrl = URL(url)
@@ -40,25 +51,29 @@ object UrlValidator {
                 val octets = match.groupValues.drop(1).map { it.toInt() }
                 
                 // Validate octets are in range 0-255
-                if (octets.any { it > 255 }) {
+                if (octets.any { it > OCTET_MAX_VALUE }) {
                     return false
                 }
                 
-                val (o1, o2, o3, o4) = octets
+                // Extract octets individually (destructuring with 4 elements triggers detekt warning)
+                val o1 = octets[0]
+                val o2 = octets[1]
                 
                 // Check RFC 1918 private IP ranges
                 return when {
                     // 10.0.0.0/8 (10.0.0.0 - 10.255.255.255)
-                    o1 == 10 -> true
+                    o1 == PRIVATE_CLASS_A_FIRST_OCTET -> true
                     
                     // 172.16.0.0/12 (172.16.0.0 - 172.31.255.255)
-                    o1 == 172 && o2 in 16..31 -> true
+                    o1 == PRIVATE_CLASS_B_FIRST_OCTET &&
+                        o2 in PRIVATE_CLASS_B_SECOND_OCTET_MIN..PRIVATE_CLASS_B_SECOND_OCTET_MAX -> true
                     
                     // 192.168.0.0/16 (192.168.0.0 - 192.168.255.255)
-                    o1 == 192 && o2 == 168 -> true
+                    o1 == PRIVATE_CLASS_C_FIRST_OCTET &&
+                        o2 == PRIVATE_CLASS_C_SECOND_OCTET -> true
                     
                     // 127.0.0.0/8 (Localhost)
-                    o1 == 127 -> true
+                    o1 == LOCALHOST_FIRST_OCTET -> true
                     
                     else -> false
                 }
@@ -67,7 +82,7 @@ object UrlValidator {
             // Not a recognized local address
             false
         } catch (e: Exception) {
-            // Invalid URL format
+            Logger.w("UrlValidator", "Failed to parse URL: ${e.message}")
             false
         }
     }

android/app/src/main/res/layout/activity_main.xml

@@ -22,6 +22,39 @@
             app:title="@string/app_name"
             app:titleTextAppearance="@style/TextAppearance.Material3.TitleLarge" />
 
+        <!-- 🔄 v1.3.1: Sync Status Banner -->
+        <LinearLayout
+            android:id="@+id/syncStatusBanner"
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content"
+            android:orientation="horizontal"
+            android:gravity="center_vertical"
+            android:paddingHorizontal="16dp"
+            android:paddingVertical="8dp"
+            android:background="?attr/colorPrimaryContainer"
+            android:visibility="gone">
+
+            <com.google.android.material.progressindicator.CircularProgressIndicator
+                android:id="@+id/syncProgressIndicator"
+                android:layout_width="24dp"
+                android:layout_height="24dp"
+                android:indeterminate="true"
+                app:indicatorSize="24dp"
+                app:trackThickness="3dp"
+                app:indicatorColor="?attr/colorOnPrimaryContainer" />
+
+            <TextView
+                android:id="@+id/syncStatusText"
+                android:layout_width="0dp"
+                android:layout_height="wrap_content"
+                android:layout_weight="1"
+                android:layout_marginStart="12dp"
+                android:text="@string/sync_status_syncing"
+                android:textAppearance="@style/TextAppearance.Material3.BodyMedium"
+                android:textColor="?attr/colorOnPrimaryContainer" />
+
+        </LinearLayout>
+
     </com.google.android.material.appbar.AppBarLayout>
 
     <!-- SwipeRefreshLayout für Pull-to-Refresh (v1.1.2) -->

android/app/src/main/res/layout/activity_settings.xml

@@ -749,6 +749,107 @@
 
             </com.google.android.material.card.MaterialCardView>
 
+            <!-- Material 3 Card: Debug Section -->
+            <com.google.android.material.card.MaterialCardView
+                android:layout_width="match_parent"
+                android:layout_height="wrap_content"
+                android:layout_marginBottom="16dp"
+                style="@style/Widget.Material3.CardView.Elevated"
+                app:cardCornerRadius="16dp">
+
+                <LinearLayout
+                    android:layout_width="match_parent"
+                    android:layout_height="wrap_content"
+                    android:orientation="vertical"
+                    android:padding="20dp">
+
+                    <!-- Section Header -->
+                    <TextView
+                        android:layout_width="match_parent"
+                        android:layout_height="wrap_content"
+                        android:text="Debug &amp; Diagnose"
+                        android:textAppearance="@style/TextAppearance.Material3.TitleMedium"
+                        android:layout_marginBottom="16dp" />
+
+                    <!-- File Logging Toggle -->
+                    <com.google.android.material.card.MaterialCardView
+                        android:layout_width="match_parent"
+                        android:layout_height="wrap_content"
+                        android:layout_marginBottom="12dp"
+                        app:cardBackgroundColor="?attr/colorSurfaceVariant"
+                        app:cardCornerRadius="12dp"
+                        app:cardElevation="0dp">
+
+                        <LinearLayout
+                            android:layout_width="match_parent"
+                            android:layout_height="wrap_content"
+                            android:orientation="horizontal"
+                            android:padding="16dp"
+                            android:gravity="center_vertical">
+
+                            <LinearLayout
+                                android:layout_width="0dp"
+                                android:layout_height="wrap_content"
+                                android:layout_weight="1"
+                                android:orientation="vertical">
+
+                                <TextView
+                                    android:layout_width="match_parent"
+                                    android:layout_height="wrap_content"
+                                    android:text="📝 Datei-Logging"
+                                    android:textAppearance="@style/TextAppearance.Material3.LabelLarge"
+                                    android:textColor="?attr/colorPrimary"
+                                    android:layout_marginBottom="4dp" />
+
+                                <TextView
+                                    android:layout_width="match_parent"
+                                    android:layout_height="wrap_content"
+                                    android:text="Sync-Logs in Datei speichern"
+                                    android:textAppearance="@style/TextAppearance.Material3.BodyMedium" />
+
+                            </LinearLayout>
+
+                            <com.google.android.material.materialswitch.MaterialSwitch
+                                android:id="@+id/switchFileLogging"
+                                android:layout_width="wrap_content"
+                                android:layout_height="wrap_content" />
+
+                        </LinearLayout>
+
+                    </com.google.android.material.card.MaterialCardView>
+
+                    <!-- F-Droid Privacy Notice -->
+                    <TextView
+                        android:layout_width="match_parent"
+                        android:layout_height="wrap_content"
+                        android:text="@string/file_logging_privacy_notice"
+                        android:textAppearance="@style/TextAppearance.Material3.BodySmall"
+                        android:textColor="?attr/colorOnSurfaceVariant"
+                        android:layout_marginBottom="16dp"
+                        android:paddingStart="4dp"
+                        android:paddingEnd="4dp" />
+
+                    <!-- Export Logs Button -->
+                    <Button
+                        android:id="@+id/buttonExportLogs"
+                        android:layout_width="match_parent"
+                        android:layout_height="wrap_content"
+                        android:text="📤 Logs exportieren &amp; teilen"
+                        style="@style/Widget.Material3.Button.TonalButton"
+                        android:layout_marginBottom="8dp" />
+
+                    <!-- Clear Logs Button -->
+                    <Button
+                        android:id="@+id/buttonClearLogs"
+                        android:layout_width="match_parent"
+                        android:layout_height="wrap_content"
+                        android:text="🗑️ Logs löschen"
+                        style="@style/Widget.Material3.Button.OutlinedButton" />
+
+                </LinearLayout>
+
+            </com.google.android.material.card.MaterialCardView>
+
         </LinearLayout>
 
     </ScrollView>

android/app/src/main/res/layout/dialog_delete_confirmation.xml

@@ -15,7 +15,7 @@
         android:layout_gravity="center_horizontal"
         android:layout_marginBottom="16dp"
         android:src="@android:drawable/ic_menu_delete"
-        android:tint="?attr/colorError"
+        app:tint="?attr/colorError"
         android:contentDescription="@string/delete" />
 
     <!-- Title -->

android/app/src/main/res/layout/item_note.xml

@@ -64,7 +64,7 @@
                 android:layout_height="18dp"
                 android:layout_gravity="center_vertical"
                 android:src="@android:drawable/ic_popup_sync"
-                android:tint="?attr/colorPrimary"
+                app:tint="?attr/colorPrimary"
                 android:contentDescription="@string/sync_status" />
 
         </LinearLayout>

android/app/src/main/res/mipmap-anydpi-v26/ic_launcher.xml

@@ -1,5 +1,5 @@
-<?xml version="1.0" encoding="utf-8"?>
 <adaptive-icon xmlns:android="http://schemas.android.com/apk/res/android">
-    <background android:drawable="@mipmap/ic_launcher_background"/>
+  <background android:drawable="@color/ic_launcher_background"/>
   <foreground android:drawable="@mipmap/ic_launcher_foreground"/>
+  <monochrome android:drawable="@mipmap/ic_launcher_monochrome"/>
 </adaptive-icon>

android/app/src/main/res/mipmap-anydpi-v26/ic_launcher_round.xml

@@ -1,5 +1,5 @@
-<?xml version="1.0" encoding="utf-8"?>
 <adaptive-icon xmlns:android="http://schemas.android.com/apk/res/android">
-    <background android:drawable="@mipmap/ic_launcher_background"/>
+  <background android:drawable="@color/ic_launcher_background"/>
   <foreground android:drawable="@mipmap/ic_launcher_foreground"/>
+  <monochrome android:drawable="@mipmap/ic_launcher_monochrome"/>
 </adaptive-icon>

android/app/src/main/res/values/colors.xml

@@ -4,6 +4,9 @@
     <color name="black">#FF000000</color>
     <color name="white">#FFFFFFFF</color>
     
+    <!-- Adaptive Icon Background -->
+    <color name="ic_launcher_background">#f9e9c8</color>
+    
     <!-- Material 3 Light Theme Colors -->
     <color name="md_theme_light_primary">#6750A4</color>
     <color name="md_theme_light_onPrimary">#FFFFFF</color>

android/app/src/main/res/values/strings.xml

@@ -57,4 +57,13 @@
     <string name="restore_progress">Stelle Notizen wieder her…</string>
     <string name="restore_success">✓ %d Notizen wiederhergestellt</string>
     <string name="restore_error">Fehler: %s</string>
+    
+    <!-- Sync Status Banner (v1.3.1) -->
+    <string name="sync_status_syncing">Synchronisiere…</string>
+    <string name="sync_status_completed">Synchronisierung abgeschlossen</string>
+    <string name="sync_status_error">Synchronisierung fehlgeschlagen</string>
+    <string name="sync_already_running">Synchronisierung läuft bereits</string>
+    
+    <!-- Debug/Logging Section (v1.3.2) -->
+    <string name="file_logging_privacy_notice">ℹ️ Datenschutz: Logs werden nur lokal auf deinem Gerät gespeichert und niemals an externe Server gesendet. Die Logs enthalten Sync-Aktivitäten zur Fehlerdiagnose. Du kannst sie jederzeit löschen oder exportieren.</string>
 </resources>

android/build.gradle.kts

@@ -2,4 +2,6 @@
 plugins {
     alias(libs.plugins.android.application) apply false
     alias(libs.plugins.kotlin.android) apply false
+    alias(libs.plugins.ktlint) apply false
+    alias(libs.plugins.detekt) apply false
 }

android/config/detekt/detekt.yml

@@ -0,0 +1,136 @@
+# ⚡ v1.3.1: detekt Configuration
+# Pragmatic rules for simple-notes-sync
+
+build:
+  maxIssues: 100  # Allow existing issues for v1.3.1 release, fix in v1.4.0
+  excludeCorrectable: false
+
+config:
+  validation: true
+  warningsAsErrors: false
+
+comments:
+  CommentOverPrivateProperty:
+    active: false
+  UndocumentedPublicClass:
+    active: false
+  UndocumentedPublicFunction:
+    active: false
+
+complexity:
+  ComplexCondition:
+    active: true
+    threshold: 5
+  CyclomaticComplexMethod:
+    active: true
+    threshold: 15
+    ignoreSingleWhenExpression: true
+  LargeClass:
+    active: true
+    threshold: 600  # Increased for WebDavSyncService
+  LongMethod:
+    active: true
+    threshold: 80  # Increased for sync methods
+  LongParameterList:
+    active: true
+    functionThreshold: 6
+    constructorThreshold: 7
+  NestedBlockDepth:
+    active: true
+    threshold: 5
+  TooManyFunctions:
+    active: true
+    thresholdInFiles: 25
+    thresholdInClasses: 25
+    thresholdInInterfaces: 20
+    thresholdInObjects: 20
+    thresholdInEnums: 10
+
+empty-blocks:
+  EmptyCatchBlock:
+    active: true
+    allowedExceptionNameRegex: "_|(ignore|expected).*"
+  EmptyFunctionBlock:
+    active: true
+    ignoreOverridden: true
+
+exceptions:
+  SwallowedException:
+    active: true
+    ignoredExceptionTypes:
+      - "InterruptedException"
+      - "MalformedURLException"
+      - "NumberFormatException"
+      - "ParseException"
+  TooGenericExceptionCaught:
+    active: true
+    exceptionNames:
+      - "Error"
+      - "Throwable"
+    allowedExceptionNameRegex: "_|(ignore|expected).*"
+
+naming:
+  FunctionNaming:
+    active: true
+    functionPattern: "[a-zA-Z][a-zA-Z0-9]*"
+  VariableNaming:
+    active: true
+    variablePattern: "[a-z][A-Za-z0-9]*"
+  PackageNaming:
+    active: true
+    packagePattern: "[a-z]+(\\.[a-z][A-Za-z0-9]*)*"
+
+performance:
+  SpreadOperator:
+    active: false  # Spread operator is fine in most cases
+
+potential-bugs:
+  CastToNullableType:
+    active: true
+  EqualsWithHashCodeExist:
+    active: true
+  UnconditionalJumpStatementInLoop:
+    active: true
+
+style:
+  ForbiddenComment:
+    active: true
+    comments:
+      - "FIXME:"
+      - "STOPSHIP:"
+    allowedPatterns: ""
+  MagicNumber:
+    active: true
+    ignoreNumbers:
+      - "-1"
+      - "0"
+      - "1"
+      - "2"
+      - "100"
+      - "1000"
+    ignoreHashCodeFunction: true
+    ignorePropertyDeclaration: true
+    ignoreLocalVariableDeclaration: true
+    ignoreAnnotation: true
+    ignoreEnums: true
+    ignoreRanges: true
+    ignoreExtensionFunctions: true
+  MaxLineLength:
+    active: true
+    maxLineLength: 120
+    excludePackageStatements: true
+    excludeImportStatements: true
+  ReturnCount:
+    active: true
+    max: 4
+    excludedFunctions: []
+    excludeLabeled: true
+    excludeReturnFromLambda: true
+    excludeGuardClauses: true
+  UnusedImports:
+    active: true
+  UnusedPrivateMember:
+    active: true
+    allowedNames: "_.*"
+  WildcardImport:
+    active: false  # Allow wildcard imports

android/gradle/libs.versions.toml

@@ -9,6 +9,8 @@ appcompat = "1.6.1"
 material = "1.10.0"
 activity = "1.8.0"
 constraintlayout = "2.1.4"
+ktlint = "12.1.0"
+detekt = "1.23.4"
 
 [libraries]
 androidx-core-ktx = { group = "androidx.core", name = "core-ktx", version.ref = "coreKtx" }
@@ -23,4 +25,6 @@ androidx-constraintlayout = { group = "androidx.constraintlayout", name = "const
 [plugins]
 android-application = { id = "com.android.application", version.ref = "agp" }
 kotlin-android = { id = "org.jetbrains.kotlin.android", version.ref = "kotlin" }
+ktlint = { id = "org.jlleitschuh.gradle.ktlint", version.ref = "ktlint" }
+detekt = { id = "io.gitlab.arturbosch.detekt", version.ref = "detekt" }
 

docs/FEATURES.en.md

@@ -130,6 +130,11 @@
 - ✅ **Password storage** - Android SharedPreferences (encrypted)
 - ✅ **No third-party libs** - Only Android SDK + Sardine (WebDAV)
 
+### Developer Features
+- ✅ **File logging** - Optional, only when enabled _(NEW in v1.3.2)_
+- ✅ **Privacy notice** - Explicit warning on activation
+- ✅ **Local logs** - Logs stay on device
+
 ---
 
 ## 🔋 Performance & Optimization
@@ -171,6 +176,7 @@
 - ✅ **Dispatchers.IO** - Background operations
 - ✅ **SharedPreferences** - Settings storage
 - ✅ **File-based storage** - JSON files locally
+- ✅ **Custom exceptions** - Dedicated SyncException for better error handling _(NEW in v1.3.2)_
 
 ### Dependencies
 - ✅ **AndroidX** - Jetpack libraries
@@ -208,27 +214,22 @@
 
 ## 🔮 Future Features
 
-Planned for upcoming versions (see [TODO.md](project-docs/simple-notes-sync/planning/TODO.md)):
+Planned for upcoming versions:
 
-### v1.3.0 - Web Editor & Organization
-- ⏳ **Browser-based editor** - Edit notes in web browser
-- ⏳ **WebDAV access via browser** - No mount needed
-- ⏳ **Mobile-optimized** - Responsive design
-- ⏳ **Offline-capable** - Progressive Web App (PWA)
-- ⏳ **Tags/labels** - Categorize notes
-- ⏳ **Search** - Full-text search in all notes
-- ⏳ **Sorting** - By date, title, tags
-- ⏳ **Filter** - Filter by tags
+### v1.4.0 - Checklists
+- ⏳ **Checklist notes** - New note type with checkboxes
+- ⏳ **Completed items** - Strike-through/check off
+- ⏳ **Drag & drop** - Reorder items
 
-### v1.4.0 - Sharing & Export
-- ⏳ **Share note** - Via share intent
-- ⏳ **Export single note** - As .txt or .md
-- ⏳ **Import from text** - Via share intent
+### v1.5.0 - Internationalization
+- ⏳ **Multi-language** - German + English UI
+- ⏳ **Language selection** - Selectable in settings
+- ⏳ **Full translation** - All strings in both languages
 
-### v1.5.0 - Advanced Editor Features
-- ⏳ **Markdown preview** - In-app rendering
-- ⏳ **Checklists** - TODO lists in notes
-- ⏳ **Syntax highlighting** - For code snippets
+### v1.6.0 - Modern APIs
+- ⏳ **Replace LocalBroadcastManager** - Use SharedFlow instead
+- ⏳ **PackageInfo Flags** - Use PackageInfoFlags.of()
+- ⏳ **Complexity refactoring** - Split long functions
 
 ---
 
@@ -271,4 +272,4 @@ A: Yes! Download the APK directly from GitHub or use F-Droid.
 
 ---
 
-**Last update:** v1.2.1 (2026-01-05)
+**Last update:** v1.3.2 (2026-01-10)

docs/FEATURES.md

@@ -130,6 +130,11 @@
 - ✅ **Passwort-Speicherung** - Android SharedPreferences (verschlüsselt)
 - ✅ **Keine Drittanbieter-Libs** - Nur Android SDK + Sardine (WebDAV)
 
+### Entwickler-Features
+- ✅ **Datei-Logging** - Optional, nur bei Aktivierung _(NEU in v1.3.2)_
+- ✅ **Datenschutz-Hinweis** - Explizite Warnung bei Aktivierung
+- ✅ **Lokale Logs** - Logs bleiben auf dem Gerät
+
 ---
 
 ## 🔋 Performance & Optimierung
@@ -171,6 +176,7 @@
 - ✅ **Dispatchers.IO** - Background-Operationen
 - ✅ **SharedPreferences** - Settings-Speicherung
 - ✅ **File-Based Storage** - JSON-Dateien lokal
+- ✅ **Custom Exceptions** - Dedizierte SyncException für bessere Fehlerbehandlung _(NEU in v1.3.2)_
 
 ### Abhängigkeiten
 - ✅ **AndroidX** - Jetpack Libraries
@@ -208,27 +214,22 @@
 
 ## 🔮 Zukünftige Features
 
-Geplant für kommende Versionen (siehe [TODO.md](project-docs/simple-notes-sync/planning/TODO.md)):
+Geplant für kommende Versionen:
 
-### v1.3.0 - Web Editor & Organisation
-- ⏳ **Browser-basierter Editor** - Notizen im Webbrowser bearbeiten
-- ⏳ **WebDAV-Zugriff via Browser** - Kein Mount nötig
-- ⏳ **Mobile-optimiert** - Responsive Design
-- ⏳ **Offline-fähig** - Progressive Web App (PWA)
-- ⏳ **Tags/Labels** - Kategorisierung von Notizen
-- ⏳ **Suche** - Volltextsuche in allen Notizen
-- ⏳ **Sortierung** - Nach Datum, Titel, Tags
-- ⏳ **Filter** - Nach Tags filtern
+### v1.4.0 - Checklisten
+- ⏳ **Checklisten-Notizen** - Neuer Notiz-Typ mit Checkboxen
+- ⏳ **Erledigte Items** - Durchstreichen/Abhaken
+- ⏳ **Drag & Drop** - Items neu anordnen
 
-### v1.4.0 - Sharing & Export
-- ⏳ **Notiz teilen** - Via Share-Intent
-- ⏳ **Einzelne Notiz exportieren** - Als .txt oder .md
-- ⏳ **Import von Text** - Via Share-Intent
+### v1.5.0 - Internationalisierung
+- ⏳ **Mehrsprachigkeit** - Deutsch + Englisch UI
+- ⏳ **Sprachauswahl** - In Einstellungen wählbar
+- ⏳ **Vollständige Übersetzung** - Alle Strings in beiden Sprachen
 
-### v1.5.0 - Erweiterte Editor-Features
-- ⏳ **Markdown-Vorschau** - In-App Rendering
-- ⏳ **Checklisten** - TODO-Listen in Notizen
-- ⏳ **Syntax-Highlighting** - Für Code-Snippets
+### v1.6.0 - Modern APIs
+- ⏳ **LocalBroadcastManager ersetzen** - SharedFlow stattdessen
+- ⏳ **PackageInfo Flags** - PackageInfoFlags.of() verwenden
+- ⏳ **Komplexitäts-Refactoring** - Lange Funktionen aufteilen
 
 ---
 
@@ -271,4 +272,4 @@ A: Ja! Lade die APK direkt von GitHub oder nutze F-Droid.
 
 ---
 
-**Letzte Aktualisierung:** v1.2.1 (2026-01-05)
+**Letzte Aktualisierung:** v1.3.2 (2026-01-10)

fastlane/metadata/android/de-DE/changelogs/10.txt

@@ -0,0 +1,5 @@
+Unter der Haube haben wir ordentlich aufgeraumt:
+- Verbesserte Sync-Performance durch optimierten Code
+- Stabilere Fehlerbehandlung bei Verbindungsproblemen
+- Speichereffizientere Datenverarbeitung
+- Datenschutz-Hinweis fur Datei-Logging hinzugefugt

fastlane/metadata/android/de-DE/changelogs/9.txt

@@ -0,0 +1,13 @@
+v1.3.1 - Multi-Device Sync Fix + Performance
+
+Multi-Device JSON Sync (Danke Thomas!):
+- JSON-Dateien syncen jetzt zwischen Geräten
+- Funktioniert auch ohne Markdown aktiviert
+- Keine doppelten Downloads mehr
+
+Performance-Verbesserungen:
+- Sync beschleunigt: 12-14s -> 2-3s
+- Erster Sync nach MD-Export jetzt schnell
+- JSON erreicht Markdown-Geschwindigkeit
+
++ Sync-Status-UI, Content MD-Import, Debug-Tools

fastlane/metadata/android/de-DE/full_description.txt

@@ -4,12 +4,14 @@ HAUPTFUNKTIONEN:
 
 • Einfache Notizen erstellen und bearbeiten
 • WebDAV-Synchronisation mit eigenem Server
+• Multi-Device Sync (Handy, Tablet, Desktop)
+• Markdown-Export für Obsidian/Desktop-Editoren
 • Automatische Synchronisation im Heim-WLAN
 • Konfigurierbares Sync-Interval (15/30/60 Minuten)
 • Transparente Batterie-Verbrauchsanzeige
 • Material Design 3 mit Dynamic Colors (Android 12+)
-• Swipe-to-Delete mit Bestätigungsdialog
-• Server-Backup & Wiederherstellung
+• Swipe-to-Delete mit Server-Sync
+• Server-Backup & Wiederherstellung (Merge/Replace/Overwrite)
 • Komplett offline nutzbar
 • Keine Werbung, keine Tracker
 
@@ -17,14 +19,23 @@ DATENSCHUTZ:
 
 Deine Daten bleiben bei dir! Die App kommuniziert nur mit deinem eigenen WebDAV-Server. Keine Cloud-Dienste, keine Tracking-Bibliotheken, keine Analysetools.
 
+MULTI-DEVICE SYNC:
+
+• Notizen synchronisieren automatisch zwischen allen Geräten
+• Lösch-Tracking verhindert "Zombie-Notizen"
+• Intelligente Konfliktlösung durch Timestamps
+• Markdown-Dateien für Desktop-Bearbeitung (Obsidian, VS Code, etc.)
+• Änderungen von Desktop-Editoren werden automatisch importiert
+
 SYNCHRONISATION:
 
 • Unterstützt alle WebDAV-Server (Nextcloud, ownCloud, etc.)
 • Konfigurierbares Interval: 15, 30 oder 60 Minuten
+• Optimierte Performance: überspringt unveränderte Dateien (~2-3s Sync-Zeit)
+• E-Tag Caching für 20x schnellere "keine Änderungen" Checks
 • Gemessener Akkuverbrauch: nur ~0.4% pro Tag (bei 30min)
 • Doze Mode optimiert für zuverlässige Background-Syncs
 • Manuelle Synchronisation jederzeit möglich
-• Konfliktfreie Zusammenführung durch Timestamps
 
 MATERIAL DESIGN 3:
 
@@ -32,6 +43,7 @@ MATERIAL DESIGN 3:
 • Dynamic Colors (Material You) auf Android 12+
 • Dark Mode Support
 • Intuitive Gesten (Swipe-to-Delete)
+• Live Sync-Status Anzeige
 
 Open Source unter MIT-Lizenz
 Quellcode: https://github.com/inventory69/simple-notes-sync

fastlane/metadata/android/en-US/changelogs/10.txt

@@ -0,0 +1,5 @@
+Under the hood improvements:
+- Improved sync performance through optimized code
+- More stable error handling for connection issues
+- More memory-efficient data processing
+- Added privacy notice for file logging

fastlane/metadata/android/en-US/changelogs/9.txt

@@ -0,0 +1,13 @@
+v1.3.1 - Multi-Device Sync Fix + Performance
+
+Multi-Device JSON Sync (Thanks Thomas!):
+- JSON files now sync between devices
+- Works without Markdown enabled
+- No duplicate downloads anymore
+
+Performance Improvements:
+- Sync speed: 12-14s -> 2-3s
+- First sync after MD export now fast
+- JSON matches Markdown speed
+
++ Sync status UI, content MD import, debug tools

fastlane/metadata/android/en-US/full_description.txt

@@ -4,12 +4,14 @@ KEY FEATURES:
 
 • Create and edit simple notes
 • WebDAV synchronization with your own server
+• Multi-device sync (phone, tablet, desktop)
+• Markdown export for Obsidian/desktop editors
 • Automatic synchronization on home WiFi
 • Configurable sync interval (15/30/60 minutes)
 • Transparent battery usage display
 • Material Design 3 with Dynamic Colors (Android 12+)
-• Swipe-to-delete with confirmation dialog
-• Server backup & restore
+• Swipe-to-delete with server sync
+• Server backup & restore (Merge/Replace/Overwrite)
 • Fully usable offline
 • No ads, no trackers
 
@@ -17,14 +19,23 @@ PRIVACY:
 
 Your data stays with you! The app only communicates with your own WebDAV server. No cloud services, no tracking libraries, no analytics tools.
 
+MULTI-DEVICE SYNC:
+
+• Notes sync automatically between all your devices
+• Deletion tracking prevents "zombie notes"
+• Smart conflict resolution through timestamps
+• Markdown files for desktop editing (Obsidian, VS Code, etc.)
+• Changes from desktop editors are auto-imported
+
 SYNCHRONIZATION:
 
 • Supports all WebDAV servers (Nextcloud, ownCloud, etc.)
 • Configurable interval: 15, 30, or 60 minutes
+• Optimized performance: skips unchanged files (~2-3s sync time)
+• E-Tag caching for 20x faster "no changes" checks
 • Measured battery consumption: only ~0.4% per day (at 30min)
 • Doze Mode optimized for reliable background syncs
 • Manual synchronization available anytime
-• Conflict-free merging through timestamps
 
 MATERIAL DESIGN 3:
 
@@ -32,6 +43,7 @@ MATERIAL DESIGN 3:
 • Dynamic Colors (Material You) on Android 12+
 • Dark Mode support
 • Intuitive gestures (Swipe-to-delete)
+• Live sync status indicator
 
 Open Source under MIT License
 Source code: https://github.com/inventory69/simple-notes-sync

metadata/dev.dettmer.simplenotes.yml

@@ -1,8 +1,8 @@
 Categories:
   - Writing
 License: MIT
-AuthorName: Liq Dettmer
-AuthorEmail: liq@dettmer.dev
+AuthorName: inventory69
+AuthorEmail: admin@dettmer.dev
 AuthorWebSite: https://dettmer.dev
 SourceCode: https://github.com/inventory69/simple-notes-sync
 IssueTracker: https://github.com/inventory69/simple-notes-sync/issues
@@ -63,7 +63,63 @@ Builds:
     scandelete:
       - android/gradle/wrapper
 
+  - versionName: 1.2.1
+    versionCode: 6
+    commit: v1.2.1
+    subdir: android/app
+    sudo:
+      - apt-get update
+      - apt-get install -y openjdk-17-jdk-headless
+      - update-java-alternatives -a
+    gradle:
+      - fdroid
+    prebuild: sed -i -e '/signingConfig/d' build.gradle.kts
+    scandelete:
+      - android/gradle/wrapper
+
+  - versionName: 1.2.2
+    versionCode: 7
+    commit: v1.2.2
+    subdir: android/app
+    sudo:
+      - apt-get update
+      - apt-get install -y openjdk-17-jdk-headless
+      - update-java-alternatives -a
+    gradle:
+      - fdroid
+    prebuild: sed -i -e '/signingConfig/d' build.gradle.kts
+    scandelete:
+      - android/gradle/wrapper
+
+  - versionName: 1.3.0
+    versionCode: 8
+    commit: v1.3.0
+    subdir: android/app
+    sudo:
+      - apt-get update
+      - apt-get install -y openjdk-17-jdk-headless
+      - update-java-alternatives -a
+    gradle:
+      - fdroid
+    prebuild: sed -i -e '/signingConfig/d' build.gradle.kts
+    scandelete:
+      - android/gradle/wrapper
+
+  - versionName: 1.3.1
+    versionCode: 9
+    commit: v1.3.1
+    subdir: android/app
+    sudo:
+      - apt-get update
+      - apt-get install -y openjdk-17-jdk-headless
+      - update-java-alternatives -a
+    gradle:
+      - fdroid
+    prebuild: sed -i -e '/signingConfig/d' build.gradle.kts
+    scandelete:
+      - android/gradle/wrapper
+
 AutoUpdateMode: Version
 UpdateCheckMode: Tags
-CurrentVersion: 1.2.0
-CurrentVersionCode: 5
+CurrentVersion: 1.3.1
+CurrentVersionCode: 9