现阶段通知中心播放暂停切换功能已实现，但是上下一曲功能暂时消失，需要后续优化，这个commit是snapshot

lib/audio/player_controller.dart

@@ -0,0 +1,33 @@
+// lib/audio/player_controller.dart
+import 'package:media_kit/media_kit.dart';
+import '../services/playback_service.dart'; // ⭐ 修正路径
+
+class PlayerController {
+  static final PlayerController _instance = PlayerController._internal();
+  factory PlayerController() => _instance;
+  PlayerController._internal();
+
+  final PlaybackService _playback = PlaybackService();
+
+  // ---- 状态流（只读） ----
+  Stream<bool> get playingStream => _playback.player.stream.playing;
+  Stream<Duration> get positionStream => _playback.player.stream.position;
+  Stream<Duration> get durationStream => _playback.player.stream.duration;
+  Stream<void> get completedStream => _playback.player.stream.completed;
+
+  // ---- 当前状态快照 ----
+  bool get isPlaying => _playback.player.state.playing;
+  Duration get position => _playback.player.state.position;
+  Duration get duration => _playback.player.state.duration;
+
+  // ---- 控制命令 ----
+  Future<void> play() => _playback.resume();
+  Future<void> pause() => _playback.pause();
+  Future<void> stop() => _playback.stop();
+  Future<void> seek(Duration position) => _playback.seek(position);
+
+  // ---- 加载歌曲 ----
+  void load(String url, {Map<String, String>? headers}) {
+    _playback.play(url, headers: headers);
+  }
+}