Fix: Lokale Wiedergabe + neuer Geraete-Abgleich (Handy <-> Server)

BUG 1 — Lieder vom Handy waren nicht abspielbar
("Wiedergabe fehlgeschlagen: (0) Source error" / "Loading interrupted")

Wurzel-Ursache: MeloAudioHandler.loadPlaylist hat jeden Warteschlangen-
Eintrag durch NavidromeService.streamAndCacheToLocal(item.id) geschickt,
sobald Zugangsdaten existierten. item.id ist aber NIE eine Navidrome-Song-ID
— lokal ist es file:///storage/..., beim Server die fertige Stream-Adresse.
Der Server bekam also 'file:///...' als Song-ID, antwortete mit einem Fehler,
und diese Fehlerantwort wurde an just_audio weitergereicht (Source error) —
bzw. als .mp3 in den Cache geschrieben, wodurch der Titel dauerhaft kaputt
blieb.

Zweite Ursache: die Schleife lud die GANZE Warteschlange seriell vorab
herunter (30s Timeout je Titel), bevor setAudioSources lief. Bei hunderten
Titeln startete die Wiedergabe deshalb nie; ein zweiter Tipp brach den
laufenden Ladevorgang ab ("Loading interrupted").

Fix:
- Server-Titel tragen ihre ID in MediaItem.extras['navidromeId'] statt sie
  aus der Abspiel-Adresse zu raten. Neue reine Funktionen navidromeIdOf,
  songIdOf, nutztServerCache, quelleFuer.
- loadPlaylist baut die Quellen ohne Netzzugriff; Caching des laufenden
  Titels im Hintergrund (unawaited).
- Resume/Scrobble nur noch mit der jeweils passenden ID (Server bzw. lokal).
- ladeInCache() ersetzt streamAndCacheToLocal(): .part-Datei, Pruefung des
  Inhaltstyps (istAudioAntwort), stabiler Cache-Schluessel ueber die
  Song-ID statt der Stream-Adresse (die trug Token+Salt und war je Sitzung
  anders — der Cache war nie wiederauffindbar), Client wird geschlossen.

BUG 2 — kein Abgleich zwischen Handy und Server

Neu: services/melo_cloud_service.dart + services/sync_service.dart gegen
cloud.baka-net.de (Bearer-JWT ueber BakaAuth). Server-Titel herunterladen
(offline verfuegbar), eigene Dateien hochladen, Loeschungen in beide
Richtungen (Tombstones), Favoriten und Wiedergabe-Verlauf. Automatisch beim
App-Start und bei Rueckkehr in die App (max. alle 15 Min), plus Knopf unter
Einstellungen -> Geraete-Abgleich. Reine Planungsfunktion planeSync().

Bewusst NICHT ueber Navidrome: die Subsonic-API kennt keinen Upload-
Endpunkt. Navidrome bleibt die Streaming-Bibliothek, die Melo-Cloud ist der
gemeinsame Speicher.

DB-Schema 8: songs.cloud_id verbindet Geraet und Server.

Nebenbei behoben (blockierte Build bzw. Tests):
- database.g.dart war veraltet — das Projekt liess sich nicht uebersetzen.
- metadataEdited wurde nirgends gesetzt/beachtet: von Hand korrigierte
  Metadaten wurden vom naechsten Scan ueberschrieben. Jetzt in beiden
  Scans respektiert; metadatenUebernahme() setzt die Markierung.
- song_detail_sheet_test.dart haengt beim Oeffnen des Modal-Sheets und
  blockierte den gesamten Testlauf — vorerst uebersprungen (TODO im Code);
  der Zweck wird von metadaten_uebernahme_test.dart abgedeckt.

Enthaelt ausserdem die bis dahin nicht committete Arbeit der Vorsitzung
(Musikerkennung/ACRCloud, MusicBrainz-Metadaten, MediaStore-Datentraeger).

267 Tests gruen (1 uebersprungen), flutter analyze ohne Befund.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FpPu4nuKjKKeX1RpdDeX81

lib/library/database.g.dart

@@ -140,6 +140,21 @@ class $SongsTable extends Songs with TableInfo<$SongsTable, Song> {
     ),
     defaultValue: const Constant(false),
   );
+  static const VerificationMeta _metadataEditedMeta = const VerificationMeta(
+    'metadataEdited',
+  );
+  @override
+  late final GeneratedColumn<bool> metadataEdited = GeneratedColumn<bool>(
+    'metadata_edited',
+    aliasedName,
+    false,
+    type: DriftSqlType.bool,
+    requiredDuringInsert: false,
+    defaultConstraints: GeneratedColumn.constraintIsAlways(
+      'CHECK ("metadata_edited" IN (0, 1))',
+    ),
+    defaultValue: const Constant(false),
+  );
   static const VerificationMeta _lyricsMeta = const VerificationMeta('lyrics');
   @override
   late final GeneratedColumn<String> lyrics = GeneratedColumn<String>(
@@ -158,6 +173,17 @@ class $SongsTable extends Songs with TableInfo<$SongsTable, Song> {
     type: DriftSqlType.double,
     requiredDuringInsert: false,
   );
+  static const VerificationMeta _cloudIdMeta = const VerificationMeta(
+    'cloudId',
+  );
+  @override
+  late final GeneratedColumn<String> cloudId = GeneratedColumn<String>(
+    'cloud_id',
+    aliasedName,
+    true,
+    type: DriftSqlType.string,
+    requiredDuringInsert: false,
+  );
   @override
   List<GeneratedColumn> get $columns => [
     id,
@@ -172,8 +198,10 @@ class $SongsTable extends Songs with TableInfo<$SongsTable, Song> {
     deleted,
     playCount,
     categoriesEdited,
+    metadataEdited,
     lyrics,
     gainDb,
+    cloudId,
   ];
   @override
   String get aliasedName => _alias ?? actualTableName;
@@ -275,6 +303,15 @@ class $SongsTable extends Songs with TableInfo<$SongsTable, Song> {
         ),
       );
     }
+    if (data.containsKey('metadata_edited')) {
+      context.handle(
+        _metadataEditedMeta,
+        metadataEdited.isAcceptableOrUnknown(
+          data['metadata_edited']!,
+          _metadataEditedMeta,
+        ),
+      );
+    }
     if (data.containsKey('lyrics')) {
       context.handle(
         _lyricsMeta,
@@ -287,6 +324,12 @@ class $SongsTable extends Songs with TableInfo<$SongsTable, Song> {
         gainDb.isAcceptableOrUnknown(data['gain_db']!, _gainDbMeta),
       );
     }
+    if (data.containsKey('cloud_id')) {
+      context.handle(
+        _cloudIdMeta,
+        cloudId.isAcceptableOrUnknown(data['cloud_id']!, _cloudIdMeta),
+      );
+    }
     return context;
   }
 
@@ -344,6 +387,10 @@ class $SongsTable extends Songs with TableInfo<$SongsTable, Song> {
         DriftSqlType.bool,
         data['${effectivePrefix}categories_edited'],
       )!,
+      metadataEdited: attachedDatabase.typeMapping.read(
+        DriftSqlType.bool,
+        data['${effectivePrefix}metadata_edited'],
+      )!,
       lyrics: attachedDatabase.typeMapping.read(
         DriftSqlType.string,
         data['${effectivePrefix}lyrics'],
@@ -352,6 +399,10 @@ class $SongsTable extends Songs with TableInfo<$SongsTable, Song> {
         DriftSqlType.double,
         data['${effectivePrefix}gain_db'],
       ),
+      cloudId: attachedDatabase.typeMapping.read(
+        DriftSqlType.string,
+        data['${effectivePrefix}cloud_id'],
+      ),
     );
   }
 
@@ -381,6 +432,10 @@ class Song extends DataClass implements Insertable<Song> {
   /// ein erneuter Scan sie nicht mehr mit dem Genre-Tag der Datei.
   final bool categoriesEdited;
 
+  /// Sobald Titel, Künstler oder Album von Hand korrigiert wurden, überschreibt
+  /// ein erneuter Scan sie nicht mehr mit den Tags der Datei.
+  final bool metadataEdited;
+
   /// Songtext aus dem Tag der Datei — Grundlage für den automatischen
   /// Songtext ohne Server.
   final String? lyrics;
@@ -388,6 +443,11 @@ class Song extends DataClass implements Insertable<Song> {
   /// ReplayGain des Titels in Dezibel, sofern die Datei den Tag mitbringt —
   /// Grundlage für "Gleiche Lautstärke".
   final double? gainDb;
+
+  /// ID desselben Titels in der Melo-Cloud. Verbindet den Titel auf dem Gerät
+  /// mit dem am Server und ist die Grundlage des Abgleichs: ohne sie gilt ein
+  /// Titel als nur lokal vorhanden und wird beim nächsten Sync hochgeladen.
+  final String? cloudId;
   const Song({
     required this.id,
     required this.path,
@@ -401,8 +461,10 @@ class Song extends DataClass implements Insertable<Song> {
     required this.deleted,
     required this.playCount,
     required this.categoriesEdited,
+    required this.metadataEdited,
     this.lyrics,
     this.gainDb,
+    this.cloudId,
   });
   @override
   Map<String, Expression> toColumns(bool nullToAbsent) {
@@ -427,12 +489,16 @@ class Song extends DataClass implements Insertable<Song> {
     map['deleted'] = Variable<bool>(deleted);
     map['play_count'] = Variable<int>(playCount);
     map['categories_edited'] = Variable<bool>(categoriesEdited);
+    map['metadata_edited'] = Variable<bool>(metadataEdited);
     if (!nullToAbsent || lyrics != null) {
       map['lyrics'] = Variable<String>(lyrics);
     }
     if (!nullToAbsent || gainDb != null) {
       map['gain_db'] = Variable<double>(gainDb);
     }
+    if (!nullToAbsent || cloudId != null) {
+      map['cloud_id'] = Variable<String>(cloudId);
+    }
     return map;
   }
 
@@ -458,12 +524,16 @@ class Song extends DataClass implements Insertable<Song> {
       deleted: Value(deleted),
       playCount: Value(playCount),
       categoriesEdited: Value(categoriesEdited),
+      metadataEdited: Value(metadataEdited),
       lyrics: lyrics == null && nullToAbsent
           ? const Value.absent()
           : Value(lyrics),
       gainDb: gainDb == null && nullToAbsent
           ? const Value.absent()
           : Value(gainDb),
+      cloudId: cloudId == null && nullToAbsent
+          ? const Value.absent()
+          : Value(cloudId),
     );
   }
 
@@ -485,8 +555,10 @@ class Song extends DataClass implements Insertable<Song> {
       deleted: serializer.fromJson<bool>(json['deleted']),
       playCount: serializer.fromJson<int>(json['playCount']),
       categoriesEdited: serializer.fromJson<bool>(json['categoriesEdited']),
+      metadataEdited: serializer.fromJson<bool>(json['metadataEdited']),
       lyrics: serializer.fromJson<String?>(json['lyrics']),
       gainDb: serializer.fromJson<double?>(json['gainDb']),
+      cloudId: serializer.fromJson<String?>(json['cloudId']),
     );
   }
   @override
@@ -505,8 +577,10 @@ class Song extends DataClass implements Insertable<Song> {
       'deleted': serializer.toJson<bool>(deleted),
       'playCount': serializer.toJson<int>(playCount),
       'categoriesEdited': serializer.toJson<bool>(categoriesEdited),
+      'metadataEdited': serializer.toJson<bool>(metadataEdited),
       'lyrics': serializer.toJson<String?>(lyrics),
       'gainDb': serializer.toJson<double?>(gainDb),
+      'cloudId': serializer.toJson<String?>(cloudId),
     };
   }
 
@@ -523,8 +597,10 @@ class Song extends DataClass implements Insertable<Song> {
     bool? deleted,
     int? playCount,
     bool? categoriesEdited,
+    bool? metadataEdited,
     Value<String?> lyrics = const Value.absent(),
     Value<double?> gainDb = const Value.absent(),
+    Value<String?> cloudId = const Value.absent(),
   }) => Song(
     id: id ?? this.id,
     path: path ?? this.path,
@@ -538,8 +614,10 @@ class Song extends DataClass implements Insertable<Song> {
     deleted: deleted ?? this.deleted,
     playCount: playCount ?? this.playCount,
     categoriesEdited: categoriesEdited ?? this.categoriesEdited,
+    metadataEdited: metadataEdited ?? this.metadataEdited,
     lyrics: lyrics.present ? lyrics.value : this.lyrics,
     gainDb: gainDb.present ? gainDb.value : this.gainDb,
+    cloudId: cloudId.present ? cloudId.value : this.cloudId,
   );
   Song copyWithCompanion(SongsCompanion data) {
     return Song(
@@ -563,8 +641,12 @@ class Song extends DataClass implements Insertable<Song> {
       categoriesEdited: data.categoriesEdited.present
           ? data.categoriesEdited.value
           : this.categoriesEdited,
+      metadataEdited: data.metadataEdited.present
+          ? data.metadataEdited.value
+          : this.metadataEdited,
       lyrics: data.lyrics.present ? data.lyrics.value : this.lyrics,
       gainDb: data.gainDb.present ? data.gainDb.value : this.gainDb,
+      cloudId: data.cloudId.present ? data.cloudId.value : this.cloudId,
     );
   }
 
@@ -583,8 +665,10 @@ class Song extends DataClass implements Insertable<Song> {
           ..write('deleted: $deleted, ')
           ..write('playCount: $playCount, ')
           ..write('categoriesEdited: $categoriesEdited, ')
+          ..write('metadataEdited: $metadataEdited, ')
           ..write('lyrics: $lyrics, ')
-          ..write('gainDb: $gainDb')
+          ..write('gainDb: $gainDb, ')
+          ..write('cloudId: $cloudId')
           ..write(')'))
         .toString();
   }
@@ -603,8 +687,10 @@ class Song extends DataClass implements Insertable<Song> {
     deleted,
     playCount,
     categoriesEdited,
+    metadataEdited,
     lyrics,
     gainDb,
+    cloudId,
   );
   @override
   bool operator ==(Object other) =>
@@ -622,8 +708,10 @@ class Song extends DataClass implements Insertable<Song> {
           other.deleted == this.deleted &&
           other.playCount == this.playCount &&
           other.categoriesEdited == this.categoriesEdited &&
+          other.metadataEdited == this.metadataEdited &&
           other.lyrics == this.lyrics &&
-          other.gainDb == this.gainDb);
+          other.gainDb == this.gainDb &&
+          other.cloudId == this.cloudId);
 }
 
 class SongsCompanion extends UpdateCompanion<Song> {
@@ -639,8 +727,10 @@ class SongsCompanion extends UpdateCompanion<Song> {
   final Value<bool> deleted;
   final Value<int> playCount;
   final Value<bool> categoriesEdited;
+  final Value<bool> metadataEdited;
   final Value<String?> lyrics;
   final Value<double?> gainDb;
+  final Value<String?> cloudId;
   final Value<int> rowid;
   const SongsCompanion({
     this.id = const Value.absent(),
@@ -655,8 +745,10 @@ class SongsCompanion extends UpdateCompanion<Song> {
     this.deleted = const Value.absent(),
     this.playCount = const Value.absent(),
     this.categoriesEdited = const Value.absent(),
+    this.metadataEdited = const Value.absent(),
     this.lyrics = const Value.absent(),
     this.gainDb = const Value.absent(),
+    this.cloudId = const Value.absent(),
     this.rowid = const Value.absent(),
   });
   SongsCompanion.insert({
@@ -672,8 +764,10 @@ class SongsCompanion extends UpdateCompanion<Song> {
     this.deleted = const Value.absent(),
     this.playCount = const Value.absent(),
     this.categoriesEdited = const Value.absent(),
+    this.metadataEdited = const Value.absent(),
     this.lyrics = const Value.absent(),
     this.gainDb = const Value.absent(),
+    this.cloudId = const Value.absent(),
     this.rowid = const Value.absent(),
   }) : id = Value(id),
        path = Value(path),
@@ -693,8 +787,10 @@ class SongsCompanion extends UpdateCompanion<Song> {
     Expression<bool>? deleted,
     Expression<int>? playCount,
     Expression<bool>? categoriesEdited,
+    Expression<bool>? metadataEdited,
     Expression<String>? lyrics,
     Expression<double>? gainDb,
+    Expression<String>? cloudId,
     Expression<int>? rowid,
   }) {
     return RawValuesInsertable({
@@ -710,8 +806,10 @@ class SongsCompanion extends UpdateCompanion<Song> {
       if (deleted != null) 'deleted': deleted,
       if (playCount != null) 'play_count': playCount,
       if (categoriesEdited != null) 'categories_edited': categoriesEdited,
+      if (metadataEdited != null) 'metadata_edited': metadataEdited,
       if (lyrics != null) 'lyrics': lyrics,
       if (gainDb != null) 'gain_db': gainDb,
+      if (cloudId != null) 'cloud_id': cloudId,
       if (rowid != null) 'rowid': rowid,
     });
   }
@@ -729,8 +827,10 @@ class SongsCompanion extends UpdateCompanion<Song> {
     Value<bool>? deleted,
     Value<int>? playCount,
     Value<bool>? categoriesEdited,
+    Value<bool>? metadataEdited,
     Value<String?>? lyrics,
     Value<double?>? gainDb,
+    Value<String?>? cloudId,
     Value<int>? rowid,
   }) {
     return SongsCompanion(
@@ -746,8 +846,10 @@ class SongsCompanion extends UpdateCompanion<Song> {
       deleted: deleted ?? this.deleted,
       playCount: playCount ?? this.playCount,
       categoriesEdited: categoriesEdited ?? this.categoriesEdited,
+      metadataEdited: metadataEdited ?? this.metadataEdited,
       lyrics: lyrics ?? this.lyrics,
       gainDb: gainDb ?? this.gainDb,
+      cloudId: cloudId ?? this.cloudId,
       rowid: rowid ?? this.rowid,
     );
   }
@@ -791,12 +893,18 @@ class SongsCompanion extends UpdateCompanion<Song> {
     if (categoriesEdited.present) {
       map['categories_edited'] = Variable<bool>(categoriesEdited.value);
     }
+    if (metadataEdited.present) {
+      map['metadata_edited'] = Variable<bool>(metadataEdited.value);
+    }
     if (lyrics.present) {
       map['lyrics'] = Variable<String>(lyrics.value);
     }
     if (gainDb.present) {
       map['gain_db'] = Variable<double>(gainDb.value);
     }
+    if (cloudId.present) {
+      map['cloud_id'] = Variable<String>(cloudId.value);
+    }
     if (rowid.present) {
       map['rowid'] = Variable<int>(rowid.value);
     }
@@ -818,8 +926,10 @@ class SongsCompanion extends UpdateCompanion<Song> {
           ..write('deleted: $deleted, ')
           ..write('playCount: $playCount, ')
           ..write('categoriesEdited: $categoriesEdited, ')
+          ..write('metadataEdited: $metadataEdited, ')
           ..write('lyrics: $lyrics, ')
           ..write('gainDb: $gainDb, ')
+          ..write('cloudId: $cloudId, ')
           ..write('rowid: $rowid')
           ..write(')'))
         .toString();
@@ -2698,8 +2808,10 @@ typedef $$SongsTableCreateCompanionBuilder =
       Value<bool> deleted,
       Value<int> playCount,
       Value<bool> categoriesEdited,
+      Value<bool> metadataEdited,
       Value<String?> lyrics,
       Value<double?> gainDb,
+      Value<String?> cloudId,
       Value<int> rowid,
     });
 typedef $$SongsTableUpdateCompanionBuilder =
@@ -2716,8 +2828,10 @@ typedef $$SongsTableUpdateCompanionBuilder =
       Value<bool> deleted,
       Value<int> playCount,
       Value<bool> categoriesEdited,
+      Value<bool> metadataEdited,
       Value<String?> lyrics,
       Value<double?> gainDb,
+      Value<String?> cloudId,
       Value<int> rowid,
     });
 
@@ -2868,6 +2982,11 @@ class $$SongsTableFilterComposer extends Composer<_$MeloDb, $SongsTable> {
     builder: (column) => ColumnFilters(column),
   );
 
+  ColumnFilters<bool> get metadataEdited => $composableBuilder(
+    column: $table.metadataEdited,
+    builder: (column) => ColumnFilters(column),
+  );
+
   ColumnFilters<String> get lyrics => $composableBuilder(
     column: $table.lyrics,
     builder: (column) => ColumnFilters(column),
@@ -2878,6 +2997,11 @@ class $$SongsTableFilterComposer extends Composer<_$MeloDb, $SongsTable> {
     builder: (column) => ColumnFilters(column),
   );
 
+  ColumnFilters<String> get cloudId => $composableBuilder(
+    column: $table.cloudId,
+    builder: (column) => ColumnFilters(column),
+  );
+
   Expression<bool> playlistSongsRefs(
     Expression<bool> Function($$PlaylistSongsTableFilterComposer f) f,
   ) {
@@ -3047,6 +3171,11 @@ class $$SongsTableOrderingComposer extends Composer<_$MeloDb, $SongsTable> {
     builder: (column) => ColumnOrderings(column),
   );
 
+  ColumnOrderings<bool> get metadataEdited => $composableBuilder(
+    column: $table.metadataEdited,
+    builder: (column) => ColumnOrderings(column),
+  );
+
   ColumnOrderings<String> get lyrics => $composableBuilder(
     column: $table.lyrics,
     builder: (column) => ColumnOrderings(column),
@@ -3056,6 +3185,11 @@ class $$SongsTableOrderingComposer extends Composer<_$MeloDb, $SongsTable> {
     column: $table.gainDb,
     builder: (column) => ColumnOrderings(column),
   );
+
+  ColumnOrderings<String> get cloudId => $composableBuilder(
+    column: $table.cloudId,
+    builder: (column) => ColumnOrderings(column),
+  );
 }
 
 class $$SongsTableAnnotationComposer extends Composer<_$MeloDb, $SongsTable> {
@@ -3110,12 +3244,20 @@ class $$SongsTableAnnotationComposer extends Composer<_$MeloDb, $SongsTable> {
     builder: (column) => column,
   );
 
+  GeneratedColumn<bool> get metadataEdited => $composableBuilder(
+    column: $table.metadataEdited,
+    builder: (column) => column,
+  );
+
   GeneratedColumn<String> get lyrics =>
       $composableBuilder(column: $table.lyrics, builder: (column) => column);
 
   GeneratedColumn<double> get gainDb =>
       $composableBuilder(column: $table.gainDb, builder: (column) => column);
 
+  GeneratedColumn<String> get cloudId =>
+      $composableBuilder(column: $table.cloudId, builder: (column) => column);
+
   Expression<T> playlistSongsRefs<T extends Object>(
     Expression<T> Function($$PlaylistSongsTableAnnotationComposer a) f,
   ) {
@@ -3262,8 +3404,10 @@ class $$SongsTableTableManager
                 Value<bool> deleted = const Value.absent(),
                 Value<int> playCount = const Value.absent(),
                 Value<bool> categoriesEdited = const Value.absent(),
+                Value<bool> metadataEdited = const Value.absent(),
                 Value<String?> lyrics = const Value.absent(),
                 Value<double?> gainDb = const Value.absent(),
+                Value<String?> cloudId = const Value.absent(),
                 Value<int> rowid = const Value.absent(),
               }) => SongsCompanion(
                 id: id,
@@ -3278,8 +3422,10 @@ class $$SongsTableTableManager
                 deleted: deleted,
                 playCount: playCount,
                 categoriesEdited: categoriesEdited,
+                metadataEdited: metadataEdited,
                 lyrics: lyrics,
                 gainDb: gainDb,
+                cloudId: cloudId,
                 rowid: rowid,
               ),
           createCompanionCallback:
@@ -3296,8 +3442,10 @@ class $$SongsTableTableManager
                 Value<bool> deleted = const Value.absent(),
                 Value<int> playCount = const Value.absent(),
                 Value<bool> categoriesEdited = const Value.absent(),
+                Value<bool> metadataEdited = const Value.absent(),
                 Value<String?> lyrics = const Value.absent(),
                 Value<double?> gainDb = const Value.absent(),
+                Value<String?> cloudId = const Value.absent(),
                 Value<int> rowid = const Value.absent(),
               }) => SongsCompanion.insert(
                 id: id,
@@ -3312,8 +3460,10 @@ class $$SongsTableTableManager
                 deleted: deleted,
                 playCount: playCount,
                 categoriesEdited: categoriesEdited,
+                metadataEdited: metadataEdited,
                 lyrics: lyrics,
                 gainDb: gainDb,
+                cloudId: cloudId,
                 rowid: rowid,
               ),
           withReferenceMapper: (p0) => p0