test(flutter): fix two latent failures exposed by un-skipping the drift cohort

Both fixes paired with the ci-flutter:3.44 rebuild that adds
libsqlite3-dev to the runner image (CI-runner push #2: libsqlite3-0
→ -dev because dart:ffi opens the unversioned .so symlink that only
the dev package ships).

widgets_smoke_test (TrackRow):
  TrackRow contains CachedIndicator which reaches
  audioCacheManagerProvider → appDbProvider → drift_flutter's
  `driftDatabase()`. That schedules a deferred-init Timer that
  outlives the test widget tree and trips the
  "A Timer is still pending after dispose" invariant. Override
  appDbProvider in the test to use AppDb(NativeDatabase.memory())
  directly — bypasses drift_flutter's Timer-using init path, still
  exercises real SQLite via FFI.

like_button_test (tap toggles + rollback):
  LikeButton was migrated to LucideHeart (SVG widget with `filled`
  bool) in the Lucide sweep; the test's `find.byIcon(Icons.favorite)`
  is stale. Replace with a small heartFilled() helper that reads
  the LucideHeart's `filled` prop straight off the widget tree.
  Same assertion semantics, just against the post-migration shape.

The four sync_controller failures need no code change — they're
the same root cause as the drift-tagged cohort (libsqlite3.so
missing → try/catch returns null → `result?.upserts` is null
instead of the expected 0). The image fix should clear them.

Fable #399 / local #62.

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

flutter_client/test/library/widgets_smoke_test.dart

@@ -1,7 +1,10 @@
+import 'package:drift/native.dart' show NativeDatabase;
 import 'package:flutter/material.dart';
 import 'package:flutter_riverpod/flutter_riverpod.dart';
 import 'package:flutter_test/flutter_test.dart';
 
+import 'package:minstrel/cache/audio_cache_manager.dart' show appDbProvider;
+import 'package:minstrel/cache/db.dart';
 import 'package:minstrel/library/widgets/album_card.dart';
 import 'package:minstrel/library/widgets/track_row.dart';
 import 'package:minstrel/models/album.dart';
@@ -29,9 +32,20 @@ void main() {
   });
 
   testWidgets('TrackRow shows mm:ss duration', (tester) async {
-    // TrackRow now contains CachedIndicator (ConsumerWidget) so a
-    // ProviderScope is required at the root.
+    // TrackRow contains CachedIndicator (ConsumerWidget) which reaches
+    // audioCacheManagerProvider → appDbProvider. Override appDbProvider
+    // with an explicit NativeDatabase.memory() executor — drift_flutter's
+    // default `driftDatabase()` schedules a deferred-init Timer that
+    // outlives the test widget tree and trips
+    // _verifyInvariants("A Timer is still pending after dispose").
     await tester.pumpWidget(ProviderScope(
+      overrides: [
+        appDbProvider.overrideWith((ref) {
+          final db = AppDb(NativeDatabase.memory());
+          ref.onDispose(db.close);
+          return db;
+        }),
+      ],
       child: MaterialApp(
         theme: buildThemeData(),
         home: Scaffold(