Fix: Review-Findings korrigiert (Tag-Leiste, Profil, Singleton u.a.)

CRIT:
- Tag-Leiste: Toggle-Kopf 'Tags & Filter' eingebaut (war unerreichbar) + TagStats
- Profil: Cloud-Count vor Dialog aufloesen (kein 'Instance of Future' mehr)
HIGH:
- CloudEinstellungen: toten Sync-Timer entfernt (echter Timer im ViewModel)
- StatistikCard + RecentWidget jetzt eingebaut (gesamtMB/gesamtMin endlich genutzt)
- CloudService als Singleton (konsistenter Token-Zustand in allen Services)
MED/LOW:
- Playlist-Erkennung nur noch via list= Parameter
- Player: fehlende Quelle wird geloggt statt still
- song_tile: null-ID-Guard vor Tag-Dialog
- Scanner-Log mit Exception-Objekt
- FavoritenService: anzahlFavoriten() fuer StatistikCard

lib/widgets/playlist_sheet.dart

@@ -118,7 +118,7 @@ class _PlaylistSheetState extends State<PlaylistSheet> {
       isScrollControlled: true,
       builder: (_) => SizedBox(
         height: MediaQuery.of(context).size.height * 0.6,
-        child: _PlaylistDetail(p: p, songs: songs, vm: widget.vm, onChanged: _laden),
+        child: _PlaylistDetail(p: p, initialSongs: songs, vm: widget.vm, onChanged: _laden),
       ),
     );
   }
@@ -172,19 +172,32 @@ class _PlaylistSheetState extends State<PlaylistSheet> {
 }
 
 /// Detailansicht einer Playlist mit Songs
-class _PlaylistDetail extends StatelessWidget {
+class _PlaylistDetail extends StatefulWidget {
   final Playlist p;
-  final List<Song> songs;
+  final List<Song> initialSongs;
   final MeloHomeViewModel vm;
   final VoidCallback onChanged;
 
   const _PlaylistDetail({
     required this.p,
-    required this.songs,
+    required this.initialSongs,
     required this.vm,
     required this.onChanged,
   });
 
+  @override
+  State<_PlaylistDetail> createState() => _PlaylistDetailState();
+}
+
+class _PlaylistDetailState extends State<_PlaylistDetail> {
+  late List<Song> _songs;
+
+  @override
+  void initState() {
+    super.initState();
+    _songs = List<Song>.from(widget.initialSongs);
+  }
+
   @override
   Widget build(BuildContext context) {
     return Padding(
@@ -209,18 +222,29 @@ class _PlaylistDetail extends StatelessWidget {
                 child: const Icon(Icons.arrow_back, size: 20, color: MeloTheme.rot),
               ),
               const SizedBox(width: 8),
-              Text(p.name, style: const TextStyle(fontSize: 16, fontWeight: FontWeight.w600, color: Colors.white)),
+              Text(widget.p.name, style: const TextStyle(fontSize: 16, fontWeight: FontWeight.w600, color: Colors.white)),
               const Spacer(),
-              Text('${songs.length} Songs', style: const TextStyle(fontSize: 12, color: MeloTheme.textSekundaer)),
+              Text('${_songs.length} Songs', style: const TextStyle(fontSize: 12, color: MeloTheme.textSekundaer)),
             ],
           ),
           const SizedBox(height: 12),
           Expanded(
-            child: songs.isEmpty
+            child: _songs.isEmpty
               ? const Center(child: Text('Playlist ist leer', style: TextStyle(fontSize: 12, color: MeloTheme.textSekundaer)))
-              : ListView.builder(
-                  itemCount: songs.length,
-                  itemBuilder: (_, i) => _songTile(context, songs[i]),
+              : ReorderableListView.builder(
+                  itemCount: _songs.length,
+                  onReorder: (oldIndex, newIndex) async {
+                    if (newIndex > oldIndex) newIndex--;
+                    setState(() {
+                      final moved = _songs.removeAt(oldIndex);
+                      _songs.insert(newIndex, moved);
+                    });
+                    if (widget.p.id != null) {
+                      await widget.vm.playlists.reihenfolgeSpeichern(widget.p.id!, _songs);
+                    }
+                    widget.onChanged();
+                  },
+                  itemBuilder: (_, i) => _songTile(context, _songs[i]),
                 ),
           ),
         ],
@@ -230,6 +254,7 @@ class _PlaylistDetail extends StatelessWidget {
 
   Widget _songTile(BuildContext context, Song song) {
     return Container(
+      key: ValueKey(song.id ?? song.dateiPfad),
       margin: const EdgeInsets.only(bottom: 4),
       padding: const EdgeInsets.symmetric(horizontal: 12, vertical: 6),
       decoration: BoxDecoration(
@@ -249,7 +274,10 @@ class _PlaylistDetail extends StatelessWidget {
           const SizedBox(width: 8),
           Expanded(
             child: GestureDetector(
-              onTap: () { Navigator.pop(context); vm.spieleSong(song); },
+              onTap: () {
+                Navigator.pop(context);
+                widget.vm.spieleSong(song, warteschlange: _songs);
+              },
               child: Column(
                 crossAxisAlignment: CrossAxisAlignment.start,
                 children: [
@@ -261,9 +289,11 @@ class _PlaylistDetail extends StatelessWidget {
           ),
           GestureDetector(
             onTap: () async {
-              await vm.playlists.songEntfernen(p.id!, song.id!);
-              onChanged();
-              if (context.mounted) Navigator.pop(context);
+              await widget.vm.playlists.songEntfernen(widget.p.id!, song.id!);
+              setState(() {
+                _songs.removeWhere((s) => s.id == song.id);
+              });
+              widget.onChanged();
             },
             child: const Icon(Icons.remove_circle_outline, size: 18, color: MeloTheme.textSekundaer),
           ),