Songtext aus Datei-Tags, Warteschlangen-Aktionen, Kategorie-Cover im

Sperrbildschirm und ReplayGain

- DB-Schema 6: lyrics + gain_db
- Songtext bevorzugt lokalen Tag, Server nur als Rueckfall; Song-ID-Bug
  beim Lyrics-Aufruf behoben
- "Als Naechstes spielen" / "Zur Warteschlange hinzufuegen" ohne Eingriff
  in Favoriten oder Wiedergabelisten
- songToMediaItem nimmt eine Cover-Vorgabe: Sperrbildschirm zeigt das
  Kategorie-Cover
- ReplayGain: Tags werden gelesen, laute Titel abgesenkt, abschaltbar

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_011snPXPafPC5i87o68H14W7

lib/playlists/playlist_detail_screen.dart

@@ -1,10 +1,12 @@
 import 'package:flutter/material.dart';
 import 'package:provider/provider.dart';
 
+import '../library/category_service.dart';
 import '../library/database.dart';
 import '../library/playlist_service.dart';
 import '../library/song_media.dart';
 import '../player/audio_handler.dart';
+import '../settings/app_settings.dart';
 import '../shared/cover.dart';
 
 /// Playlist-Detailansicht: Songs anzeigen, per Drag & Drop umsortieren, entfernen.
@@ -17,6 +19,8 @@ class PlaylistDetailScreen extends StatelessWidget {
     final db = context.read<MeloDb>();
     final handler = context.read<MeloAudioHandler>();
     final service = context.read<PlaylistService>();
+    final categories = context.watch<CategoryService>();
+    final settings = context.watch<AppSettings>();
     return Scaffold(
       appBar: AppBar(title: Text(playlist.name)),
       body: StreamBuilder<List<Song>>(
@@ -47,11 +51,15 @@ class PlaylistDetailScreen extends StatelessWidget {
               final s = songs[i];
               return ListTile(
                 key: ValueKey(s.id),
-                leading: CoverImage(
-                  artUri: s.coverPath != null ? Uri.file(s.coverPath!) : null,
-                  size: 48,
-                  radius: 6,
-                ),
+                leading: Builder(builder: (context) {
+                  final cover = categories.coverFor(s,
+                      groupByCategory: settings.groupCoversByCategory);
+                  return CoverImage(
+                    artUri: cover != null ? Uri.file(cover) : null,
+                    size: 48,
+                    radius: 6,
+                  );
+                }),
                 title: Text(s.title, maxLines: 1, overflow: TextOverflow.ellipsis),
                 subtitle: Text(s.artist ?? 'Unbekannt',
                     maxLines: 1, overflow: TextOverflow.ellipsis),
@@ -62,7 +70,13 @@ class PlaylistDetailScreen extends StatelessWidget {
                 ),
                 onTap: () async {
                   try {
-                    await playSongs(handler, songs, i);
+                    await playSongs(
+                      handler,
+                      songs,
+                      i,
+                      coverOf: (song) => categories.coverFor(song,
+                          groupByCategory: settings.groupCoversByCategory),
+                    );
                   } catch (e) {
                     if (context.mounted) {
                       ScaffoldMessenger.of(context).showSnackBar(