perf(player): narrow now-playing queue sheet to shuffle-mode selector

The sheet watched the whole playbackStateProvider, which re-emits every 500ms
during playback, rebuilding the entire ReorderableListView twice a second just
to recompute an unchanged shuffle toggle. Watch a .select of shuffleMode only.

lib/screens/now_playing_screen.dart

@@ -741,9 +741,11 @@ class _NowPlayingScreenState extends ConsumerState<NowPlayingScreen> {
                 final queue = ref.watch(playQueueProvider).value ?? const [];
                 final current = ref.watch(currentMediaItemProvider).value;
                 final controller = ref.read(musicPlayerControllerProvider);
-                final shuffleOn =
-                    ref.watch(playbackStateProvider).value?.shuffleMode ==
-                    AudioServiceShuffleMode.all;
+                final shuffleOn = ref.watch(
+                  playbackStateProvider.select(
+                    (s) => s.value?.shuffleMode == AudioServiceShuffleMode.all,
+                  ),
+                );
                 final textTheme = Theme.of(context).textTheme;
 
                 return Column(