v2.55.3 — Code-Review-Fixes: foregroundServiceType (Android 14+), POST_NOTIFICATIONS-Check, FG-Service-Notification-Channel, try/catch _zeigeSyncNotification

CRITICAL:
- AndroidManifest: foregroundServiceType="dataSync" für BackgroundService (Android 14+ MissingForegroundServiceTypeException)
- main.dart: notificationChannelId + initialNotificationTitle + foregroundServiceTypes für FlutterBackgroundService (fehlende FG-Notification → ANR/crash nach 5s)

MEDIUM:
- sync_service.dart: POST_NOTIFICATIONS-Permission-Check vor _starteForegroundService (Android 13+)
- sync_service.dart: try/catch um _zeigeSyncNotification (plugin-dispose-Sicherheit)

flutter analyze: clean | flutter test: 194/194 passed

lib/main.dart

@@ -77,12 +77,33 @@ void main() async {
       ?.createNotificationChannel(syncChannel);
 
   // ── Background Service initialisieren (Issue #3) ──
+  // v2.55.3: Foreground-Service-Notification-Channel konfigurieren.
+  // Ohne notificationChannelId zeigt der Service eine Default-Notification
+  // ohne eigenen Channel — auf Android 14+ Pflicht.
+  const fgChannel = AndroidNotificationChannel(
+    'de.baka.melo.fg_service',
+    'Melo Hintergrunddienst',
+    description: 'Hält Melo im Hintergrund aktiv (Sync, Downloads)',
+    importance: Importance.low,
+    playSound: false,
+    enableVibration: false,
+    showBadge: false,
+  );
+  await notificationsPlugin
+      .resolvePlatformSpecificImplementation<
+          AndroidFlutterLocalNotificationsPlugin>()
+      ?.createNotificationChannel(fgChannel);
+
   await FlutterBackgroundService().configure(
     iosConfiguration: IosConfiguration(),
     androidConfiguration: AndroidConfiguration(
       onStart: _onServiceStart,
       autoStart: false,
       isForegroundMode: true,
+      notificationChannelId: 'de.baka.melo.fg_service',
+      initialNotificationTitle: 'Melo Sync',
+      initialNotificationContent: 'Synchronisiere Musik…',
+      foregroundServiceTypes: [AndroidForegroundType.dataSync],
     ),
   );