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/library/widgets/compact_track_card.dart

@@ -4,6 +4,7 @@ import 'package:flutter_riverpod/flutter_riverpod.dart';
 import '../../models/track.dart';
 import '../../player/player_provider.dart';
 import '../../shared/widgets/server_image.dart';
+import '../../shared/widgets/track_actions/track_actions_button.dart';
 import '../../theme/theme_extension.dart';
 
 /// Small horizontal track cell used by the home Most-played section.
@@ -74,6 +75,7 @@ class CompactTrackCard extends ConsumerWidget {
                 ],
               ),
             ),
+            TrackActionsButton(track: track),
           ]),
         ),
       ),