fix: Android 9 crash - Implement getForegroundInfo() for WorkManager Expedited Work (Issue #15)

This commit fixes the critical crash on Android 9 (API 28) that occurred when using
WorkManager Expedited Work for background sync operations.

## Root Cause
When setExpedited() is used in WorkManager, the CoroutineWorker must implement
getForegroundInfo() to return a ForegroundInfo object with a Foreground Service
notification. On Android 9-11, WorkManager calls this method, but the default
implementation throws: IllegalStateException: Not implemented

## Solution
- Implemented getForegroundInfo() in SyncWorker
- Returns ForegroundInfo with sync progress notification
- Android 10+: Sets FOREGROUND_SERVICE_TYPE_DATA_SYNC for proper service typing
- Added required Foreground Service permissions to AndroidManifest.xml

## Technical Changes
- SyncWorker.kt: Added getForegroundInfo() override
- NotificationHelper.kt: Added createSyncProgressNotification() factory method
- strings.xml: Added sync_in_progress UI strings (EN + DE)
- AndroidManifest.xml: Added FOREGROUND_SERVICE permissions
- Version updated to 1.7.1 (versionCode 18)

## Previously Fixed (in this release)
- Kernel-VPN compatibility (Wireguard interface detection)
- HTTP connection lifecycle optimization (SafeSardineWrapper)
- Stability improvements for sync sessions

## Testing
- Tested on Android 9 (API 28) - No crash on second app start
- Tested on Android 15 (API 35) - No regressions
- WiFi-connect sync working correctly
- Expedited work notifications display properly

Fixes #15
Thanks to @roughnecks for detailed bug report and testing!

android/app/src/main/AndroidManifest.xml

@@ -12,6 +12,11 @@
     <!-- Battery Optimization (for WorkManager background sync) -->
     <uses-permission android:name="android.permission.REQUEST_IGNORE_BATTERY_OPTIMIZATIONS" />
     
+    <!-- v1.7.2: Foreground Service for Expedited Work (Android 9-11) -->
+    <uses-permission android:name="android.permission.FOREGROUND_SERVICE" />
+    <!-- v1.7.2: Foreground Service Type for Android 10+ -->
+    <uses-permission android:name="android.permission.FOREGROUND_SERVICE_DATA_SYNC" />
+    
     <!-- BOOT Permission - CRITICAL für Auto-Sync nach Neustart! -->
     <uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED" />
 

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

@@ -5,8 +5,11 @@ package dev.dettmer.simplenotes.sync
 import android.app.ActivityManager
 import android.content.Context
 import android.content.Intent
+import android.content.pm.ServiceInfo
+import android.os.Build
 import androidx.localbroadcastmanager.content.LocalBroadcastManager
 import androidx.work.CoroutineWorker
+import androidx.work.ForegroundInfo
 import androidx.work.WorkerParameters
 import dev.dettmer.simplenotes.BuildConfig
 import dev.dettmer.simplenotes.utils.Constants
@@ -26,6 +29,35 @@ class SyncWorker(
         const val ACTION_SYNC_COMPLETED = "dev.dettmer.simplenotes.SYNC_COMPLETED"
     }
     
+    /**
+     * 🔧 v1.7.2: Required for expedited work on Android 9-11
+     * 
+     * WorkManager ruft diese Methode auf um die Foreground-Notification zu erstellen
+     * wenn der Worker als Expedited Work gestartet wird.
+     * 
+     * Ab Android 12+ wird diese Methode NICHT aufgerufen (neue Expedited API).
+     * Auf Android 9-11 MUSS diese Methode implementiert sein!
+     * 
+     * @see https://developer.android.com/develop/background-work/background-tasks/persistent/getting-started/define-work#foregroundinfo
+     */
+    override suspend fun getForegroundInfo(): ForegroundInfo {
+        val notification = NotificationHelper.createSyncProgressNotification(applicationContext)
+        
+        // Android 10+ benötigt foregroundServiceType
+        return if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q) {
+            ForegroundInfo(
+                NotificationHelper.SYNC_PROGRESS_NOTIFICATION_ID,
+                notification,
+                ServiceInfo.FOREGROUND_SERVICE_TYPE_DATA_SYNC
+            )
+        } else {
+            ForegroundInfo(
+                NotificationHelper.SYNC_PROGRESS_NOTIFICATION_ID,
+                notification
+            )
+        }
+    }
+    
     /**
      * Prüft ob die App im Vordergrund ist.
      * Wenn ja, brauchen wir keine Benachrichtigung - die UI zeigt die Änderungen direkt.

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

@@ -19,6 +19,7 @@ object NotificationHelper {
     private const val CHANNEL_ID = "notes_sync_channel"
     private const val NOTIFICATION_ID = 1001
     private const val SYNC_NOTIFICATION_ID = 2
+    const val SYNC_PROGRESS_NOTIFICATION_ID = 1003  // v1.7.2: For expedited work foreground notification
     private const val AUTO_CANCEL_TIMEOUT_MS = 30_000L
     
     /**
@@ -54,6 +55,26 @@ object NotificationHelper {
         Logger.d(TAG, "🗑️ Cleared old sync notifications")
     }
     
+    /**
+     * 🔧 v1.7.2: Erstellt Notification für Sync-Progress (Expedited Work)
+     * 
+     * Wird von SyncWorker.getForegroundInfo() aufgerufen auf Android 9-11.
+     * Muss eine gültige, sichtbare Notification zurückgeben.
+     * 
+     * @return Notification (nicht anzeigen, nur erstellen)
+     */
+    fun createSyncProgressNotification(context: Context): android.app.Notification {
+        return NotificationCompat.Builder(context, CHANNEL_ID)
+            .setSmallIcon(android.R.drawable.stat_notify_sync)
+            .setContentTitle(context.getString(R.string.sync_in_progress))
+            .setContentText(context.getString(R.string.sync_in_progress_text))
+            .setPriority(NotificationCompat.PRIORITY_LOW)
+            .setOngoing(true)
+            .setProgress(0, 0, true)  // Indeterminate progress
+            .setCategory(NotificationCompat.CATEGORY_PROGRESS)
+            .build()
+    }
+    
     /**
      * Zeigt Erfolgs-Notification nach Sync
      */

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

@@ -438,6 +438,8 @@
     <!-- ============================= -->
     <string name="notification_channel_name">Notizen Synchronisierung</string>
     <string name="notification_channel_desc">Benachrichtigungen über Sync-Status</string>
+    <string name="sync_in_progress">Synchronisierung läuft</string>
+    <string name="sync_in_progress_text">Notizen werden synchronisiert…</string>
     <string name="notification_sync_success_title">Sync erfolgreich</string>
     <string name="notification_sync_success_message">%d Notiz(en) synchronisiert</string>
     <string name="notification_sync_failed_title">Sync fehlgeschlagen</string>

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

@@ -438,6 +438,8 @@
     <!-- ============================= -->
     <string name="notification_channel_name">Notes Synchronization</string>
     <string name="notification_channel_desc">Notifications about sync status</string>
+    <string name="sync_in_progress">Syncing</string>
+    <string name="sync_in_progress_text">Syncing notes…</string>
     <string name="notification_sync_success_title">Sync successful</string>
     <string name="notification_sync_success_message">%d note(s) synchronized</string>
     <string name="notification_sync_failed_title">Sync failed</string>