feat(playlist): 歌单变更与歌单内元数据实时刷新

两个边界场景：
1) 新建/重命名/删除歌单、加入/移除歌曲后，主页歌单页不刷新
2) 歌单详情页里歌曲补全元数据后，标题/封面不更新

- 新增 PlaylistEvents（void 事件）
- PlaylistRepository 的创建/重命名/删除/批量加入/移除后 publish
- 主页订阅后重新拉取歌单摘要
- 歌单详情页订阅 MetadataEvents，按 path 就地更新行

lib/pages/home_page.dart

@@ -4,6 +4,7 @@ import 'package:provider/provider.dart';
 import '../services/audio_service.dart';
 import '../services/favorite_events.dart';
 import '../services/metadata_events.dart';
+import '../services/playlist_events.dart';
 import '../services/webdav_service.dart';
 import '../widgets/magnetic_scroll_physics.dart';
 import 'webdav_setup_page.dart';
@@ -168,6 +169,7 @@ class _HomePageState extends BaseState<HomePage> {
   final PageController _homePageController = PageController();
   StreamSubscription<MetadataUpdate>? _metaSub;
   StreamSubscription<String>? _favSub;
+  StreamSubscription<void>? _plSub;
   List<PlaylistSummary> _playlistSummaries = [];
 
   // ========== 滚动控制 ==========
@@ -207,6 +209,7 @@ class _HomePageState extends BaseState<HomePage> {
     _scrollController = ScrollController()..addListener(_onScroll);
     _metaSub = MetadataEvents().stream.listen(_onMetadataUpdate);
     _favSub = FavoriteEvents().stream.listen((_) => _onFavoriteChanged());
+    _plSub = PlaylistEvents().stream.listen((_) => _onPlaylistChanged());
     _initWebDAV();
 
     WidgetsBinding.instance.addPostFrameCallback((_) {
@@ -218,6 +221,7 @@ class _HomePageState extends BaseState<HomePage> {
   void dispose() {
     _metaSub?.cancel();
     _favSub?.cancel();
+    _plSub?.cancel();
     _homePageController.dispose();
     _scrollController.dispose();
     super.dispose();
@@ -249,6 +253,12 @@ class _HomePageState extends BaseState<HomePage> {
     }
   }
 
+  /// 歌单数据变化后刷新歌单页
+  Future<void> _onPlaylistChanged() async {
+    await _loadPlaylistSummaries();
+    if (mounted) safeSetState(() {});
+  }
+
   /// 任何位置收藏/取消收藏后，重新拉一次收藏列表
   Future<void> _onFavoriteChanged() async {
     await _loadFavoritesFromDb();

lib/pages/playlist_detail_page.dart

@@ -1,3 +1,4 @@
+import 'dart:async';
 // lib/pages/playlist_detail_page.dart
 import 'package:flutter/material.dart';
 import 'package:provider/provider.dart';
@@ -5,6 +6,7 @@ import 'package:provider/provider.dart';
 import '../database/song_database.dart';
 import '../repositories/playlist_repository.dart';
 import '../services/audio_service.dart';
+import '../services/metadata_events.dart';
 import '../widgets/song_artwork.dart';
 
 /// 歌单详情：展示歌单内歌曲，支持播放全部 / 单曲播放 / 移除
@@ -41,14 +43,40 @@ class _PlaylistDetailPageState extends State<PlaylistDetailPage> {
   final SongDatabase _db = SongDatabase();
 
   List<_SongRow> _songs = [];
+  StreamSubscription<MetadataUpdate>? _metaSub;
   bool _loading = true;
 
   @override
   void initState() {
     super.initState();
+    _metaSub = MetadataEvents().stream.listen(_onMetadataUpdate);
     _load();
   }
 
+  @override
+  void dispose() {
+    _metaSub?.cancel();
+    super.dispose();
+  }
+
+  /// 歌单里的歌补全元数据后，就地更新对应行
+  void _onMetadataUpdate(MetadataUpdate update) {
+    final index = _songs.indexWhere((item) => item.path == update.path);
+    if (index < 0 || !mounted) return;
+    final row = update.row;
+    final title = (row['title'] as String?)?.trim() ?? '';
+    final artist = (row['artist'] as String?)?.trim() ?? '';
+    final artwork = (row['artwork_path'] as String?)?.trim() ?? '';
+    final old = _songs[index];
+    setState(() {
+      _songs[index] = _SongRow(
+        path: old.path,
+        title: title.isNotEmpty ? title : old.title,
+        artist: artist.isNotEmpty ? artist : old.artist,
+        artworkPath: artwork.isNotEmpty ? artwork : old.artworkPath,
+      );
+    });
+  }
   Future<void> _load() async {
     setState(() => _loading = true);
     try {

lib/repositories/playlist_repository.dart

@@ -3,6 +3,7 @@ import 'dart:math';
 import '../database/song_database.dart';
 import '../models/playlist.dart';
 import '../models/playlist_summary.dart';
+import '../services/playlist_events.dart';
 import '../services/audio_service.dart';
 
 class PlaylistRepository {
@@ -35,6 +36,7 @@ class PlaylistRepository {
   Future<Playlist> createPlaylist(String name) async {
     final playlist = Playlist(id: _generateId(), name: name);
     await _db.insertPlaylist(playlist.toJson());
+    PlaylistEvents().publish();
     return playlist;
   }
 
@@ -55,6 +57,7 @@ class PlaylistRepository {
       existing.add(id);
       added++;
     }
+    if (added > 0) PlaylistEvents().publish();
     return added;
   }
   Future<void> updatePlaylistName(String id, String newName) async {
@@ -62,6 +65,7 @@ class PlaylistRepository {
       'name': newName,
       'updated_at': DateTime.now().millisecondsSinceEpoch,
     });
+    PlaylistEvents().publish();
   }
 
   // ⭐ 新增：更新播放模式
@@ -78,6 +82,7 @@ class PlaylistRepository {
 
   Future<void> deletePlaylist(String id) async {
     await _db.deletePlaylist(id);
+    PlaylistEvents().publish();
   }
 
   // ════════════════════════════════════════════════════════════
@@ -95,6 +100,7 @@ class PlaylistRepository {
 
   Future<void> removeSong(String playlistId, String songId) async {
     await _db.removeSongFromPlaylist(playlistId, songId);
+    PlaylistEvents().publish();
   }
 
   Future<void> reorderSongs(

lib/services/playlist_events.dart

@@ -0,0 +1,21 @@
+// lib/services/playlist_events.dart
+import 'dart:async';
+
+/// 歌单数据变更事件（新建/重命名/删除/加歌/删歌/排序）。
+///
+/// 主页的歌单页、歌单详情页都靠它实时刷新，
+/// 不用等页面重建。
+class PlaylistEvents {
+  static final PlaylistEvents _instance = PlaylistEvents._internal();
+  factory PlaylistEvents() => _instance;
+  PlaylistEvents._internal();
+
+  final StreamController<void> _controller =
+      StreamController<void>.broadcast();
+
+  Stream<void> get stream => _controller.stream;
+
+  void publish() {
+    _controller.add(null);
+  }
+}