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/player/now_playing_screen.dart

@@ -2,6 +2,8 @@ import 'package:flutter/material.dart';
 import 'package:flutter_riverpod/flutter_riverpod.dart';
 import 'package:go_router/go_router.dart';
 
+import '../models/track.dart';
+import '../shared/widgets/track_actions/track_actions_button.dart';
 import '../theme/theme_extension.dart';
 import 'player_provider.dart';
 
@@ -46,7 +48,28 @@ class NowPlayingScreen extends ConsumerWidget {
               width: 280, height: 280, color: fs.slate,
             ),
             const SizedBox(height: 24),
-            Text(media.title, style: TextStyle(color: fs.parchment, fontSize: 22)),
+            Row(mainAxisAlignment: MainAxisAlignment.center, children: [
+              Flexible(
+                child: Text(
+                  media.title,
+                  style: TextStyle(color: fs.parchment, fontSize: 22),
+                  overflow: TextOverflow.ellipsis,
+                ),
+              ),
+              TrackActionsButton(
+                track: TrackRef(
+                  id: media.id,
+                  title: media.title,
+                  albumId: (media.extras?['album_id'] as String?) ?? '',
+                  albumTitle: media.album ?? '',
+                  artistId: '', // not stashed in MediaItem.extras today
+                  artistName: media.artist ?? '',
+                  durationSec: media.duration?.inSeconds ?? 0,
+                  streamUrl: '',
+                ),
+                hideQueueActions: true,
+              ),
+            ]),
             Text(media.artist ?? '', style: TextStyle(color: fs.ash, fontSize: 14)),
             const SizedBox(height: 16),
             Slider(