fix(flutter): analyze errors after Plan B push

Cleared 5 errors + 1 warning + 1 info from CI flutter analyze on 5114a81:

- prefetcher.dart: Riverpod listener callbacks used (_, _) for two
  placeholder params — Dart 3 enforces unique names. Changed to (_, __).
- prefetcher.dart: Riverpod 3's AsyncValue exposes `.value` (nullable)
  not `.valueOrNull`. Three call sites updated.
- sync_controller.dart: doc comment had `?since=<cursor>` → analyzer
  warned about unintended HTML. Wrapped in backticks with `{cursor}`.
- sync_controller.dart: delete loop over heterogeneous Table list
  inferred as List<Table>; drift's delete() expects TableInfo. Unrolled
  to explicit per-table deletes.
- audio_cache_manager_test.dart: db.into(...).insertAll([...]) doesn't
  exist on InsertStatement — only insert/insertOnConflictUpdate. Used
  db.batch((b) => b.insertAll(table, [...])) instead, in two test cases.
- audio_handler.dart: LockCachingAudioSource is marked experimental in
  just_audio. Added // ignore: experimental_member_use — operator
  acknowledged the experimental status during brainstorming and we're
  the project; CI's --fatal-infos would otherwise gate.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

flutter_client/lib/cache/prefetcher.dart

@@ -18,18 +18,18 @@ class Prefetcher {
     // The mediaItem stream changes whenever the active track changes
     // (skipNext/skipPrev or natural progression). Settings changes (e.g.
     // operator bumps prefetch window) also trigger a reconcile.
-    _ref.listen<AsyncValue<MediaItem?>>(mediaItemProvider, (_, _) => _reconcile());
+    _ref.listen<AsyncValue<MediaItem?>>(mediaItemProvider, (_, __) => _reconcile());
-    _ref.listen<AsyncValue<CacheSettings>>(cacheSettingsProvider, (_, _) => _reconcile());
+    _ref.listen<AsyncValue<CacheSettings>>(cacheSettingsProvider, (_, __) => _reconcile());
   }
 
   final Ref _ref;
 
   Future<void> _reconcile() async {
-    final settings = _ref.read(cacheSettingsProvider).valueOrNull;
+    final settings = _ref.read(cacheSettingsProvider).value;
     if (settings == null) return;
 
-    final queue = _ref.read(queueProvider).valueOrNull ?? const <MediaItem>[];
+    final queue = _ref.read(queueProvider).value ?? const <MediaItem>[];
-    final current = _ref.read(mediaItemProvider).valueOrNull;
+    final current = _ref.read(mediaItemProvider).value;
     if (queue.isEmpty || current == null) return;
 
     final currentIdx = queue.indexWhere((m) => m.id == current.id);

flutter_client/lib/cache/sync_controller.dart

@@ -19,7 +19,7 @@ class SyncResult {
 }
 
 /// Drives the delta-sync against the server (#357 Plan A endpoint).
-/// Reads cursor from drift, calls /api/library/sync?since=<cursor>,
+/// Reads cursor from drift, calls `/api/library/sync?since={cursor}`,
 /// applies upserts + deletes, advances cursor.
 class SyncController extends AsyncNotifier<SyncResult?> {
   @override
@@ -55,16 +55,12 @@ class SyncController extends AsyncNotifier<SyncResult?> {
       // local state and retry once with cursor=0.
       if (resp.statusCode == 410) {
         await db.transaction(() async {
-          for (final t in [
+          await db.delete(db.cachedArtists).go();
-            db.cachedArtists,
+          await db.delete(db.cachedAlbums).go();
-            db.cachedAlbums,
+          await db.delete(db.cachedTracks).go();
-            db.cachedTracks,
+          await db.delete(db.cachedLikes).go();
-            db.cachedLikes,
+          await db.delete(db.cachedPlaylists).go();
-            db.cachedPlaylists,
+          await db.delete(db.cachedPlaylistTracks).go();
-            db.cachedPlaylistTracks,
-          ]) {
-            await db.delete(t).go();
-          }
           await db.into(db.syncMetadata).insertOnConflictUpdate(
                 SyncMetadataCompanion.insert(cursor: const drift.Value(0)),
               );

flutter_client/lib/player/audio_handler.dart

@@ -114,6 +114,7 @@ class MinstrelAudioHandler extends BaseAudioHandler with QueueHandler, SeekHandl
       final cacheFile = File('${cacheDir.path}/audio_cache/${t.id}.mp3');
       debugPrint('audio_handler: cache miss for track.id=${t.id}, '
           'using LockCachingAudioSource → ${cacheFile.path}');
+      // ignore: experimental_member_use
       return LockCachingAudioSource(parsed,
           headers: headers, cacheFile: cacheFile);
     }

flutter_client/test/cache/audio_cache_manager_test.dart

@@ -31,12 +31,20 @@ void main() {
       dioFactory: () async => Dio(),
       cacheDirFactory: () async => tmp,
     );
-    await db.into(db.audioCacheIndex).insertAll([
+    await db.batch((b) {
+      b.insertAll(db.audioCacheIndex, [
         AudioCacheIndexCompanion.insert(
-          trackId: 'a', path: 'p', sizeBytes: 100, source: CacheSource.manual),
+            trackId: 'a',
+            path: 'p',
+            sizeBytes: 100,
+            source: CacheSource.manual),
         AudioCacheIndexCompanion.insert(
-          trackId: 'b', path: 'p', sizeBytes: 250, source: CacheSource.incidental),
+            trackId: 'b',
+            path: 'p',
+            sizeBytes: 250,
+            source: CacheSource.incidental),
       ]);
+    });
     expect(await mgr.usageBytes(), 350);
   });
 
@@ -55,7 +63,8 @@ void main() {
     final f2 = File('${tmp.path}/audio_cache/man.mp3');
     await f2.create(recursive: true);
     await f2.writeAsBytes(List.filled(100, 0));
-    await db.into(db.audioCacheIndex).insertAll([
+    await db.batch((b) {
+      b.insertAll(db.audioCacheIndex, [
         AudioCacheIndexCompanion.insert(
             trackId: 'inc',
             path: f1.path,
@@ -67,6 +76,7 @@ void main() {
             sizeBytes: 100,
             source: CacheSource.manual),
       ]);
+    });
     expect(await mgr.usageBytes(), 200);
     await mgr.evict(targetBytes: 100);
     expect(await mgr.isCached('inc'), false);