🚀 feat: Production release preparation with GitHub Actions deployment

## Major Features
- ✅ Battery optimized auto-sync (30 min interval, ~0.4%/day)
- ✅ BuildConfig.DEBUG conditional logging (Logger.kt)
- ✅ Settings UI cleanup (SSID field removed)
- ✅ Interactive notifications (click opens app)
- ✅ Post-reboot auto-sync (BootReceiver)
- ✅ GitHub Actions deployment workflow

## Implementation Details

### Auto-Sync Architecture
- WorkManager PeriodicWorkRequest (30 min intervals)
- Gateway IP detection via network interface enumeration
- Smart sync only when on home network
- BootReceiver restarts monitoring after device reboot

### Logging System
- Logger.kt object with BuildConfig.DEBUG checks
- Debug logs only in DEBUG builds
- Error/warning logs always visible
- All components updated (NetworkMonitor, SyncWorker, WebDavSyncService, etc.)

### UI Improvements
- Removed confusing SSID field from Settings
- Gateway detection fully automatic
- Material Design 3 info boxes
- Cleaner, simpler user interface

### Notifications
- PendingIntent opens MainActivity on click
- setAutoCancel(true) for auto-dismiss
- Broadcast receiver for UI refresh on sync

### GitHub Actions
- Automated APK builds on push to main
- Signed releases with proper keystore
- 3 APK variants (universal, arm64-v8a, armeabi-v7a)
- Semantic versioning: YYYY.MM.DD + build number
- Comprehensive release notes with installation guide

## Documentation
- README.md: User-friendly German guide
- DOCS.md: Technical architecture documentation
- GITHUB_ACTIONS_SETUP.md: Deployment setup guide

## Build Configuration
- Signing support via key.properties
- APK splits for smaller downloads
- ProGuard enabled with resource shrinking
- BuildConfig generation for DEBUG flag

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

@@ -1,7 +1,7 @@
 package dev.dettmer.simplenotes
 
 import android.app.Application
-import android.util.Log
+import dev.dettmer.simplenotes.utils.Logger
 import dev.dettmer.simplenotes.sync.NetworkMonitor
 import dev.dettmer.simplenotes.utils.NotificationHelper
 
@@ -11,31 +11,34 @@ class SimpleNotesApplication : Application() {
         private const val TAG = "SimpleNotesApp"
     }
     
-    private lateinit var networkMonitor: NetworkMonitor
+    lateinit var networkMonitor: NetworkMonitor  // Public access für SettingsActivity
     
     override fun onCreate() {
         super.onCreate()
         
-        Log.d(TAG, "🚀 Application onCreate()")
+        Logger.d(TAG, "🚀 Application onCreate()")
         
         // Initialize notification channel
         NotificationHelper.createNotificationChannel(this)
-        Log.d(TAG, "✅ Notification channel created")
+        Logger.d(TAG, "✅ Notification channel created")
         
-        // Initialize and start NetworkMonitor at application level
-        // CRITICAL: Use applicationContext, not 'this'!
+        // Initialize NetworkMonitor (WorkManager-based)
+        // VORTEIL: WorkManager läuft auch ohne aktive App!
         networkMonitor = NetworkMonitor(applicationContext)
+        
+        // Start WorkManager periodic sync
+        // Dies läuft im Hintergrund auch wenn App geschlossen ist
         networkMonitor.startMonitoring()
         
-        Log.d(TAG, "✅ NetworkMonitor initialized and started")
+        Logger.d(TAG, "✅ WorkManager-based auto-sync initialized")
     }
     
     override fun onTerminate() {
         super.onTerminate()
         
-        Log.d(TAG, "🛑 Application onTerminate()")
+        Logger.d(TAG, "🛑 Application onTerminate()")
         
-        // Clean up NetworkMonitor when app is terminated
-        networkMonitor.stopMonitoring()
+        // WorkManager läuft weiter auch nach onTerminate!
+        // Nur bei deaktiviertem Auto-Sync stoppen wir es
     }
 }