v1.5.0: Jetpack Compose Settings Redesign + Fixes

Features:
- ✨ Complete Settings UI redesign with Jetpack Compose
- 🎨 Material 3 Design with Dynamic Colors (Material You)
- 📊 6 logical settings groups in separate screens:
  * Server Settings (URL, Credentials, Connection Test)
  * Sync Settings (Auto-Sync, Interval 15/30/60 min)
  * Markdown Desktop Integration (Auto-Sync for .md files)
  * Backup & Restore (Local/Server)
  * About this App (Version, GitHub, License)
  * Debug & Diagnostics (File Logging, Log Export)

Bugfixes (ported from old SettingsActivity):
- 🔧 Fix #1: Server URL prefix (http://|https://) auto-set on init
- 🔧 Fix #2: Battery optimization dialog on Auto-Sync enable
- 🔧 Fix #3: Markdown initial export on feature activation

Implementation Details:
- SettingsViewModel with Kotlin Flows state management
- SettingsEvent system for Activity-level actions (dialogs, intents)
- Reusable Compose components (SettingsCard, Switch, RadioGroup, etc.)
- Progress dialog for markdown initial export
- Edge-to-edge display with system bar handling
- Navigation Compose for screen transitions with back button

Breaking Changes:
- Old SettingsActivity.kt (1147 lines) no longer used
  (Can be removed in future as legacy code)

android/app/src/main/AndroidManifest.xml

@@ -43,11 +43,17 @@
             android:windowSoftInputMode="adjustResize"
             android:parentActivityName=".MainActivity" />
 
-        <!-- Settings Activity -->
+        <!-- Settings Activity (Legacy - XML-based) -->
         <activity
             android:name=".SettingsActivity"
             android:parentActivityName=".MainActivity" />
 
+        <!-- Settings Activity v1.5.0 (Jetpack Compose) -->
+        <activity
+            android:name=".ui.settings.ComposeSettingsActivity"
+            android:parentActivityName=".MainActivity"
+            android:theme="@style/Theme.SimpleNotes" />
+
         <!-- Boot Receiver - Startet WorkManager nach Reboot -->
         <receiver
             android:name=".sync.BootReceiver"