修复webdav重新登录后，userID位置错位与页面跳转逻辑错误的重大bug

lib/pages/webdav_setup_page.dart

@@ -35,7 +35,7 @@ class _WebDAVSetupPageState extends BaseState<WebDAVSetupPage> {
 
   Future<void> _loadSavedCredentials() async {
     final hasCred = await WebDAVService.instance.loadCredentials();
-    setState(() {
+    safeSetState(() {
       _isConnected = hasCred;
       _statusText = hasCred ? '已连接' : '未连接';
       if (hasCred) {
@@ -47,7 +47,7 @@ class _WebDAVSetupPageState extends BaseState<WebDAVSetupPage> {
   Future<void> _connect() async {
     if (!_formKey.currentState!.validate()) return;
 
-    setState(() => _isLoading = true);
+    safeSetState(() => _isLoading = true);
 
     try {
       await WebDAVService.instance.saveCredentials(
@@ -59,7 +59,7 @@ class _WebDAVSetupPageState extends BaseState<WebDAVSetupPage> {
       // 验证连接
       await WebDAVService.instance.getMusicFiles();
 
-      setState(() {
+      safeSetState(() {
         _isConnected = true;
         _statusText = '已连接';
         _isLoading = false;
@@ -72,7 +72,8 @@ class _WebDAVSetupPageState extends BaseState<WebDAVSetupPage> {
             backgroundColor: Color(0xFF4CAF50),
           ),
         );
-        // ✅ 登录成功 → 直接跳转到文件列表页
+        // ⭐ 用 pushReplacement 替换当前页面（WebDAVSetupPage）
+        // 此时栈底是 HomePage，替换后栈变为 [HomePage, WebDAVFileListPage]
         Navigator.pushReplacement(
           context,
           MaterialPageRoute(
@@ -81,7 +82,7 @@ class _WebDAVSetupPageState extends BaseState<WebDAVSetupPage> {
         );
       }
     } catch (e) {
-      setState(() {
+      safeSetState(() {
         _isConnected = false;
         _statusText = '连接失败';
         _isLoading = false;
@@ -99,7 +100,7 @@ class _WebDAVSetupPageState extends BaseState<WebDAVSetupPage> {
 
   Future<void> _disconnect() async {
     await WebDAVService.instance.clearCredentials();
-    setState(() {
+    safeSetState(() {
       _isConnected = false;
       _statusText = '未连接';
     });