feat(flutter): full parity for player bar — shuffle/repeat/volume + Like + kebab + 3-column layout (#356)

Mirrors web's compact PlayerBar both visually (3-column top + full-
width seek bottom) and functionally — closes parity gaps that had
been hidden because the prior mini-bar surfaced none of these
controls.

### audio_handler.dart

- Override `setShuffleMode` → delegates to just_audio's
  `setShuffleModeEnabled`.
- Override `setRepeatMode` → maps audio_service modes (none/one/all/
  group) to just_audio's LoopMode (off/one/all).
- New `setVolume(double)` + `volumeStream` getter (audio_service's
  PlaybackState doesn't carry volume — surface it separately).
- `_broadcastState` now populates PlaybackState's shuffleMode +
  repeatMode fields, and re-fires on shuffle/repeat/loop stream
  changes so UI subscribers stay in sync.

### player_provider.dart

- New `volumeProvider` (StreamProvider<double>).
- `PlayerActions` gains `toggleShuffle()`, `cycleRepeat()` (none →
  all → one → none), and `setVolume(double)`.

### player_bar.dart

Complete rebuild matching the operator-designed layout:

  ┌──────────┬───────────┬──────────────────┐
  │ art      │ ♥   ⋮     │ 🔀 🔁 ☰           │  ← short row
  │ title    │           │                  │
  │ artist   │ ⏮  ⏯  ⏭   │ volume slider    │  ← play row, full size
  ├──────────┴───────────┴──────────────────┤
  │ 0:42 ━━━━━●━━━━━━━━━━━━━━━━━━━━━ 3:21  │
  └─────────────────────────────────────────┘

- Column 1 (35%): cover + title + artist. Tap → /now-playing.
- Column 2 (intrinsic): like + kebab on top, play controls (40/48/40)
  on bottom.
- Column 3 (30%): shuffle/repeat/queue on top, volume slider on bottom.
- Bottom: full-width seek slider with mm:ss labels.

`TrackActionsButton` reused for the kebab; reconstructs a minimal
TrackRef from MediaItem extras (same pattern NowPlayingScreen
already uses).

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

flutter_client/lib/player/audio_handler.dart

@@ -14,6 +14,10 @@ class MinstrelAudioHandler extends BaseAudioHandler with QueueHandler, SeekHandl
   MinstrelAudioHandler() {
     _player.playbackEventStream.listen(_broadcastState);
     _player.currentIndexStream.listen(_onCurrentIndexChanged);
+    // Re-broadcast on shuffle/repeat changes so the PlaybackState's
+    // shuffleMode + repeatMode fields stay current for UI subscribers.
+    _player.shuffleModeEnabledStream.listen((_) => _broadcastState(null));
+    _player.loopModeStream.listen((_) => _broadcastState(null));
   }
 
   final AudioPlayer _player = AudioPlayer();
@@ -22,6 +26,11 @@ class MinstrelAudioHandler extends BaseAudioHandler with QueueHandler, SeekHandl
   AlbumCoverCache? _coverCache;
   AudioCacheManager? _audioCacheManager;
 
+  /// Volume stream for UI subscribers. Mirrors the just_audio player's
+  /// volume directly; set via setVolume(double).
+  Stream<double> get volumeStream => _player.volumeStream;
+  double get volume => _player.volume;
+
   void configure({
     required String baseUrl,
     required String? token,
@@ -198,7 +207,34 @@ class MinstrelAudioHandler extends BaseAudioHandler with QueueHandler, SeekHandl
   @override
   Future<void> skipToPrevious() => _player.seekToPrevious();
 
-  void _broadcastState(PlaybackEvent event) {
+  @override
+  Future<void> setShuffleMode(AudioServiceShuffleMode shuffleMode) async {
+    await _player
+        .setShuffleModeEnabled(shuffleMode != AudioServiceShuffleMode.none);
+    // _broadcastState picks up the change via shuffleModeEnabledStream.
+  }
+
+  @override
+  Future<void> setRepeatMode(AudioServiceRepeatMode repeatMode) async {
+    final loop = switch (repeatMode) {
+      AudioServiceRepeatMode.none => LoopMode.off,
+      AudioServiceRepeatMode.one => LoopMode.one,
+      AudioServiceRepeatMode.all || AudioServiceRepeatMode.group => LoopMode.all,
+    };
+    await _player.setLoopMode(loop);
+  }
+
+  /// Sets player volume in [0.0, 1.0]. Note: most mobile browsers tie
+  /// page audio to system volume — this is the in-app slider for parity
+  /// with desktop/web; on mobile the system volume is the real control.
+  Future<void> setVolume(double v) async {
+    await _player.setVolume(v.clamp(0.0, 1.0));
+  }
+
+  // _broadcastState accepts a nullable event because the shuffle/repeat
+  // listeners don't have one — we just want to re-emit PlaybackState
+  // with up-to-date shuffleMode/repeatMode fields.
+  void _broadcastState(PlaybackEvent? event) {
     final playing = _player.playing;
     playbackState.add(PlaybackState(
       controls: [
@@ -218,7 +254,15 @@ class MinstrelAudioHandler extends BaseAudioHandler with QueueHandler, SeekHandl
       updatePosition: _player.position,
       bufferedPosition: _player.bufferedPosition,
       speed: _player.speed,
-      queueIndex: event.currentIndex,
+      queueIndex: event?.currentIndex ?? _player.currentIndex,
+      shuffleMode: _player.shuffleModeEnabled
+          ? AudioServiceShuffleMode.all
+          : AudioServiceShuffleMode.none,
+      repeatMode: switch (_player.loopMode) {
+        LoopMode.off => AudioServiceRepeatMode.none,
+        LoopMode.one => AudioServiceRepeatMode.one,
+        LoopMode.all => AudioServiceRepeatMode.all,
+      },
     ));
   }
 }