🌟 Feature: Favoriten-Sync vom Navidrome-Server (Phase 2, Part 4/X)

- syncFavoritesFromServer() in PlaylistService laden Server-Favoriten
- Prüft lokal existierende Songs und markiert als Favorit
- Settings-Button: "🌟 Favoriten-Sync" mit Cloud-Download Icon
- Zeigt Anzahl importierter Favoriten mit SnackBar
- DB-Methoden hinzugefügt: songExists() + setFavorite()

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01XJzQjUtnvYUtHdnTs3iCru

lib/settings/settings_screen.dart

@@ -3,6 +3,7 @@ import 'package:provider/provider.dart';
 
 import '../library/database.dart';
 import '../library/permissions.dart';
+import '../library/playlist_service.dart';
 import '../services/cache_manager.dart';
 import '../services/navidrome_service.dart';
 import '../services/offline_mode.dart';
@@ -103,6 +104,16 @@ class _SettingsScreenState extends State<SettingsScreen> {
                   )
                 : null,
           ),
+          ListTile(
+            leading: const Icon(Icons.favorite),
+            title: const Text('🌟 Favoriten-Sync'),
+            subtitle: const Text('Favoriten vom Server importieren'),
+            trailing: IconButton(
+              tooltip: 'Vom Server laden',
+              icon: const Icon(Icons.cloud_download),
+              onPressed: () => _syncServerFavorites(),
+            ),
+          ),
           const Divider(height: 1),
           const _SectionLabel('Berechtigungen'),
           ListTile(
@@ -242,6 +253,28 @@ class _SettingsScreenState extends State<SettingsScreen> {
     }
   }
 
+  Future<void> _syncServerFavorites() async {
+    final playlistService = context.read<PlaylistService>();
+    if (!mounted) return;
+
+    ScaffoldMessenger.of(context).showSnackBar(
+      const SnackBar(content: Text('Lade Favoriten vom Server...')),
+    );
+
+    final count = await playlistService.syncFavoritesFromServer();
+    if (mounted) {
+      if (count == 0) {
+        ScaffoldMessenger.of(context).showSnackBar(
+          const SnackBar(content: Text('❌ Server nicht verbunden oder keine Favoriten')),
+        );
+      } else {
+        ScaffoldMessenger.of(context).showSnackBar(
+          SnackBar(content: Text('✅ $count Favoriten importiert')),
+        );
+      }
+    }
+  }
+
   String _formatBytes(int bytes) {
     if (bytes < 1024) return '$bytes B';
     if (bytes < 1024 * 1024) return '${(bytes / 1024).toStringAsFixed(1)} KB';