v2.41 — Issue #3: Musik-Download im Hintergrund (flutter_background_service)

- flutter_background_service ^5.0.0 hinzugefügt
- AndroidManifest: FOREGROUND_SERVICE_DATA_SYNC Permission
- main.dart: Background Service mit configure() initialisiert
- _onServiceStart(): Service-Callback für Foreground-Garantie
- DownloadService._startBackgroundService(): Foreground Service vor Download
- DownloadService._stopBackgroundService(): Stopp nach Batch/Single
- Integration in _resetStatus, downloadBatch, downloadVonUrl

lib/main.dart

@@ -5,6 +5,7 @@ import 'package:audio_service/audio_service.dart';
 import 'package:shared_preferences/shared_preferences.dart';
 import 'package:permission_handler/permission_handler.dart';
 import 'package:flutter_local_notifications/flutter_local_notifications.dart';
+import 'package:flutter_background_service/flutter_background_service.dart';
 import 'database/db_helper.dart';
 import 'services/favoriten_service.dart';
 import 'services/auth_service.dart';
@@ -47,6 +48,16 @@ void main() async {
           AndroidFlutterLocalNotificationsPlugin>()
       ?.createNotificationChannel(downloadChannel);
 
+  // ── Background Service initialisieren (Issue #3) ──
+  await FlutterBackgroundService().configure(
+    iosConfiguration: IosConfiguration(),
+    androidConfiguration: AndroidConfiguration(
+      onStart: _onServiceStart,
+      autoStart: false,
+      isForegroundMode: true,
+    ),
+  );
+
   try {
     await DbHelper().db;
     await FavoritenService().init();
@@ -148,6 +159,19 @@ Future<void> _starteAutoSyncFallsNoetig() async {
   }
 }
 
+/// Background Service Callback – hält App im Vordergrund beim Download (Issue #3)
+@pragma('vm:entry-point')
+Future<bool> _onServiceStart(ServiceInstance service) async {
+  WidgetsFlutterBinding.ensureInitialized();
+  // Service läuft als Foreground-Service und hält den Prozess am Leben.
+  // Der eigentliche Download läuft im Haupt-Isolate – der Service dient nur
+  // als WakeLock / Foreground-Garantie.
+  service.on('stopService').listen((_) {
+    service.stopSelf();
+  });
+  return true;
+}
+
 class MeloApp extends StatelessWidget {
   const MeloApp({super.key});