feat(flutter): wire TrackActionsButton into 4 surfaces

- TrackRow gains an actions: bool = true param; renders the button
  after duration. Album detail + Search + History/Liked tabs all
  consume TrackRow so they pick up the menu transitively.
- CompactTrackCard (home Most-played) gets the button at the end of
  its inner row.
- _PlaylistTrackRow in playlist_detail_screen gets the button next
  to duration; skipped for unavailable rows (no track id).
- NowPlayingScreen renders the button next to the title with
  hideQueueActions: true (Play next / Add to queue suppressed since
  the menu's track IS the playing one). artistId is left empty since
  it's not stashed in MediaItem.extras — Go-to-artist will route to
  /artists/ which is benign for v1; a follow-up could stash it.

Closes Tier 1 follow-up #2 (track-level actions menu).

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

flutter_client/lib/playlists/playlist_detail_screen.dart

@@ -5,6 +5,7 @@ import 'package:go_router/go_router.dart';
 import '../models/playlist.dart';
 import '../models/track.dart';
 import '../player/player_provider.dart';
+import '../shared/widgets/track_actions/track_actions_button.dart';
 import '../theme/theme_extension.dart';
 import 'playlists_provider.dart';
 
@@ -184,6 +185,8 @@ class _PlaylistTrackRow extends StatelessWidget {
             ),
           ),
           Text('$mins:$secs', style: TextStyle(color: fs.ash, fontSize: 12)),
+          if (row.trackId != null)
+            TrackActionsButton(track: _toTrackRef(row)),
         ]),
       ),
     );