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/song_tile.dart

@@ -1,7 +1,9 @@
+import 'dart:io';
 import 'package:flutter/material.dart';
 import '../models/song.dart';
 import '../utils/farb_theme.dart';
 import 'metadaten_dialog.dart';
+import 'tag_auswahl_dialog.dart';
 
 class SongTile extends StatelessWidget {
   final Song song;
@@ -10,6 +12,7 @@ class SongTile extends StatelessWidget {
   final ValueChanged<Song> onPlay;
   final VoidCallback onMetadataChanged;
   final ValueChanged<Song>? onAddToPlaylist;
+  final ValueChanged<Song>? onDelete;
 
   const SongTile({
     super.key,
@@ -19,20 +22,26 @@ class SongTile extends StatelessWidget {
     required this.onPlay,
     required this.onMetadataChanged,
     this.onAddToPlaylist,
+    this.onDelete,
   });
 
   @override
   Widget build(BuildContext context) {
     final hatDatei = song.dateiPfad.isNotEmpty;
+    final hatCover = song.coverPfad != null && File(song.coverPfad!).existsSync();
     return ListTile(
       contentPadding: const EdgeInsets.symmetric(vertical: 2),
-      leading: Container(
-        width: 44, height: 44,
-        decoration: BoxDecoration(
-          borderRadius: BorderRadius.circular(10),
-          gradient: const LinearGradient(colors: [Color(0xFF1A0000), Color(0xFF660000)]),
+      leading: ClipRRect(
+        borderRadius: BorderRadius.circular(10),
+        child: Container(
+          width: 44, height: 44,
+          decoration: const BoxDecoration(
+            gradient: LinearGradient(colors: [Color(0xFF1A0000), Color(0xFF660000)]),
+          ),
+          child: hatCover
+              ? Image.file(File(song.coverPfad!), fit: BoxFit.cover)
+              : const Center(child: Text('♪', style: TextStyle(fontSize: 18, color: Colors.white54))),
         ),
-        child: const Center(child: Text('♪', style: TextStyle(fontSize: 18, color: Colors.white54))),
       ),
       title: Text(song.titel, style: const TextStyle(fontSize: 14, fontWeight: FontWeight.w500, color: Colors.white)),
       subtitle: Text(song.kuenstler, style: const TextStyle(fontSize: 12, color: MeloTheme.textSekundaer)),
@@ -53,6 +62,26 @@ class SongTile extends StatelessWidget {
               child: Icon(Icons.edit, size: 14, color: MeloTheme.textSekundaer),
             ),
           ),
+          InkWell(
+            borderRadius: BorderRadius.circular(50),
+            onTap: () {
+              // Guard gegen null-ID (defensive)
+              final id = song.id;
+              if (id == null) return;
+              showDialog(
+                context: context,
+                builder: (_) => TagAuswahlDialog(
+                  songId: id,
+                  songTitel: song.titel,
+                  onChanged: onMetadataChanged,
+                ),
+              );
+            },
+            child: Padding(
+              padding: const EdgeInsets.all(6),
+              child: const Icon(Icons.label_outline, size: 14, color: MeloTheme.textSekundaer),
+            ),
+          ),
           if (onAddToPlaylist != null)
             InkWell(
               borderRadius: BorderRadius.circular(50),
@@ -77,6 +106,39 @@ class SongTile extends StatelessWidget {
         ],
       ),
       onTap: hatDatei ? () => onPlay(song) : null,
+      onLongPress: onDelete != null ? () {
+        showModalBottomSheet(
+          context: context,
+          backgroundColor: MeloTheme.dunkel1,
+          builder: (ctx) => SafeArea(
+            child: Column(
+              mainAxisSize: MainAxisSize.min,
+              children: [
+                ListTile(
+                  leading: const Icon(Icons.edit, color: Colors.white),
+                  title: const Text('Bearbeiten', style: TextStyle(color: Colors.white)),
+                  onTap: () async {
+                    Navigator.pop(ctx);
+                    final geaendert = await showDialog<bool>(
+                      context: context,
+                      builder: (_) => MetadatenDialog(song: song),
+                    );
+                    if (geaendert == true) onMetadataChanged();
+                  },
+                ),
+                ListTile(
+                  leading: const Icon(Icons.delete, color: Colors.red),
+                  title: const Text('Löschen', style: TextStyle(color: Colors.red)),
+                  onTap: () {
+                    Navigator.pop(ctx);
+                    onDelete!(song);
+                  },
+                ),
+              ],
+            ),
+          ),
+        );
+      } : null,
     );
   }
 }