fix(ui): 加入歌单弹层不再被迷你播放器遮挡

原因：迷你播放器挂在 Navigator overlay 上，层级高于底部弹层，
弹层里的歌单列表被它盖住，看起来像"没读到歌单"。
（日志确认查询正常：读到 1 个歌单）

- RouteManager 抽到 services/route_manager.dart，新增临时隐藏开关
- 打开"加入歌单"弹层时隐藏迷你播放器，关闭后恢复
- main.dart 的 shouldShow 改用 showMiniPlayer（原来直接读路由，开关不生效）
- 弹层底部加 SafeArea minimum + 16px 余量，不再贴着手势区

真机验证：弹层正常显示 "TL / 1 首"，底部留出安全距离。

lib/main.dart

@@ -7,6 +7,7 @@ import 'package:permission_handler/permission_handler.dart';
 
 import 'package:flutter/services.dart';
 import 'services/audio_service.dart';
+import 'services/route_manager.dart';
 import 'services/playback_service.dart';
 import 'services/app_lifecycle_service.dart';
 import 'services/webdav_service.dart';
@@ -107,28 +108,6 @@ void main() async {
   });
 }
 
-// ════════════════════════════════════════════════════════════
-// 路由管理器（控制 MiniPlayer 显示/隐藏）
-// ════════════════════════════════════════════════════════════
-class RouteManager extends ChangeNotifier {
-  static final RouteManager _instance = RouteManager._internal();
-  factory RouteManager() => _instance;
-  RouteManager._internal();
-
-  String _currentRoute = '/';
-  String get currentRoute => _currentRoute;
-
-  bool get showMiniPlayer =>
-      _currentRoute != '/player' && _currentRoute != '/playlist';
-
-  void updateRoute(String route) {
-    if (_currentRoute != route) {
-      _currentRoute = route;
-      debugPrint('📌 路由更新: $route');
-      notifyListeners();
-    }
-  }
-}
 
 // ════════════════════════════════════════════════════════════
 // 导航观察者（监听路由变化）
@@ -399,8 +378,7 @@ class _QTPlayerAppState extends State<QTPlayerApp> {
                 animation: RouteManager(),
                 builder: (context, _) {
                   final routeManager = RouteManager();
-                  final shouldShow = routeManager.currentRoute != '/player' &&
-                      routeManager.currentRoute != '/playlist';
+                  final shouldShow = routeManager.showMiniPlayer;
 
                   return AnimatedSwitcher(
                     duration: const Duration(milliseconds: 300),
@@ -436,4 +414,4 @@ class _QTPlayerAppState extends State<QTPlayerApp> {
       ),
     );
   }
-}
+}