页面层级与返回逻辑实现完成，并且去掉web相关代码支持

lib/pages/player_page.dart

@@ -1,19 +1,10 @@
-// lib/pages/player_page.dart
 import 'package:flutter/material.dart';
 import 'package:provider/provider.dart';
 import '../services/audio_service.dart';
 import '../main.dart';
-import 'playlist_page.dart';
 
 class PlayerPage extends StatefulWidget {
-  final VoidCallback onClose;
-  final VoidCallback onOpenPlaylist;
-
-  const PlayerPage({
-    super.key,
-    required this.onClose,
-    required this.onOpenPlaylist,
-  });
+  const PlayerPage({super.key});
 
   @override
   State<PlayerPage> createState() => _PlayerPageState();
@@ -37,22 +28,33 @@ class _PlayerPageState extends State<PlayerPage> {
     if (song == null) {
       return Scaffold(
         backgroundColor: const Color(0xFF0E1211),
-        body: Center(
+        appBar: AppBar(
+          backgroundColor: Colors.transparent,
+          elevation: 0,
+          leading: IconButton(
+            icon: const Icon(Icons.arrow_back_ios_new, color: Colors.white),
+            onPressed: () => Navigator.pop(context),
+          ),
+          title: const Text(
+            '正在播放',
+            style: TextStyle(color: Colors.white, fontSize: 16),
+          ),
+          centerTitle: true,
+        ),
+        body: const Center(
           child: Column(
             mainAxisAlignment: MainAxisAlignment.center,
             children: [
-              const Text(
+              Icon(Icons.music_off, size: 64, color: Colors.grey),
+              SizedBox(height: 16),
+              Text(
                 '没有正在播放的歌曲',
                 style: TextStyle(color: Colors.grey),
               ),
-              const SizedBox(height: 16),
-              ElevatedButton(
-                onPressed: widget.onClose,
-                style: ElevatedButton.styleFrom(
-                  backgroundColor: const Color(0xFFB8D4D0),
-                  foregroundColor: Colors.black87,
-                ),
-                child: const Text('返回'),
+              SizedBox(height: 16),
+              Text(
+                '请先在首页点击一首歌曲',
+                style: TextStyle(color: Colors.grey, fontSize: 12),
               ),
             ],
           ),
@@ -83,7 +85,7 @@ class _PlayerPageState extends State<PlayerPage> {
         elevation: 0,
         leading: IconButton(
           icon: const Icon(Icons.arrow_back_ios_new, color: Colors.white),
-          onPressed: widget.onClose,
+          onPressed: () => Navigator.pop(context),
         ),
         title: const Text(
           '正在播放',
@@ -279,8 +281,8 @@ class _PlayerPageState extends State<PlayerPage> {
                 Container(
                   width: 56,
                   height: 56,
-                  decoration: BoxDecoration(
-                    color: const Color(0xFFB8D4D0),
+                  decoration: const BoxDecoration(
+                    color: Color(0xFFB8D4D0),
                     shape: BoxShape.circle,
                   ),
                   child: IconButton(
@@ -301,7 +303,9 @@ class _PlayerPageState extends State<PlayerPage> {
                   padding: const EdgeInsets.all(12),
                 ),
                 IconButton(
-                  onPressed: widget.onOpenPlaylist,
+                  onPressed: () {
+                    navigatorKey.currentState?.pushNamed('/playlist');
+                  },
                   icon: const Icon(
                     Icons.playlist_play_outlined,
                     color: Color(0xFFB8D4D0),