feat: add app update checks and standalone release publishing panel

mobile/lib/features/profile/profile_page.dart

@@ -24,6 +24,8 @@ class ProfilePage extends StatelessWidget {
     this.logoutLabel = '退出学校登录',
     this.onUpdateTerm,
     this.feedbackSender = const UnconfiguredFeedbackSender(),
+    this.onCheckUpdates,
+    this.checkingUpdates = false,
   });
   final AppController controller;
   final VoidCallback onLogin;
@@ -32,6 +34,8 @@ class ProfilePage extends StatelessWidget {
   final VoidCallback? onUpdateTerm;
   final String authStatus, logoutLabel;
   final FeedbackSender feedbackSender;
+  final VoidCallback? onCheckUpdates;
+  final bool checkingUpdates;
   Future<void> _import(BuildContext context) async {
     try {
       final file = await FilePicker.pickFile(
@@ -231,6 +235,32 @@ class ProfilePage extends StatelessWidget {
                   ),
                 ),
               ),
+              Divider(height: 1, color: ink.withValues(alpha: 0.06)),
+              ListTile(
+                key: const Key('check-app-update'),
+                contentPadding: EdgeInsets.zero,
+                leading: const Icon(
+                  Icons.system_update_rounded,
+                  color: river,
+                  size: 23,
+                ),
+                title: const Text(
+                  '检查更新',
+                  style: TextStyle(fontSize: 14, fontWeight: FontWeight.w600),
+                ),
+                subtitle: Text(
+                  checkingUpdates ? '正在检查…' : '当前版本 $appVersion',
+                  style: const TextStyle(fontSize: 11),
+                ),
+                trailing: checkingUpdates
+                    ? const SizedBox(
+                        width: 18,
+                        height: 18,
+                        child: CircularProgressIndicator(strokeWidth: 2),
+                      )
+                    : const Icon(Icons.chevron_right_rounded),
+                onTap: checkingUpdates ? null : onCheckUpdates,
+              ),
             ],
           ),
         ),