feat: 实验性连接信息导出与会话恢复，重写关于页

- SessionShare：把 userId / JSESSIONID / token 打成 Base64(JSON)，Cookie 只保留
  JSESSIONID 一项，粘贴时容忍换行与空白，QR 令牌与乱码解不出来
- 主页底部新增「导出连接信息」卡片，标记实验性：内容未加密，字符串在手即可操作账号
- 登录页识别到连接信息时把登录按钮换成「恢复会话」，不必再扫 QR 令牌
- 恢复优先沿用导入的 JSESSIONID（不重发 UserLoginApi，免得顶掉机台上的登录），
  Cookie 失效才退回用 token 登录；验证 Cookie 时顺手拉到的 GetUserDataApi 结果
  直接交给主页展示，省一次请求
- 仅凭 Cookie 恢复的会话没有 loginId / loginDateTime，_gameLogin 保持 null，
  票据与风险页照旧提示「尚未登录游戏服务器」，主页顶部给出说明横幅
- 关于页改用 AppCard / SectionTitle 脚手架，补基本信息与风险提示，把过时的
  「jsQR (web)」致谢换成原生 MethodChannel（QR 解码早已不走 web 库）

lib/pages/login_page.dart

@@ -3,12 +3,16 @@ import 'package:flutter/material.dart';
 import '../config/responsive.dart';
 import '../config/strings.dart';
 import '../models/session_model.dart';
+import '../models/session_share.dart';
 import '../services/file_picker_service.dart';
 import '../services/qr_service.dart';
+import '../widgets/app_notice.dart';
 import 'home_page.dart';
 import 'settings_page.dart';
 
 /// 登录页：粘贴 / 识别 QR 令牌，走 Aime 登录后进入主页。
+///
+/// 也接受主页导出的「连接信息」（实验性）：那是一串 Base64，直接续上原有会话。
 class LoginPage extends StatefulWidget {
   const LoginPage({super.key});
 
@@ -19,6 +23,7 @@ class LoginPage extends StatefulWidget {
 class _LoginPageState extends State<LoginPage> {
   final _qrController = TextEditingController();
   String _qrCode = '';
+  SessionShare? _share;
   bool _loading = false;
   bool _forcePreviewApi = false;
 
@@ -29,8 +34,10 @@ class _LoginPageState extends State<LoginPage> {
   }
 
   void _onQRContentChanged(String value) {
+    final text = value.trim();
     setState(() {
-      _qrCode = SessionModel.extractQRCode(value.trim());
+      _qrCode = SessionModel.extractQRCode(text);
+      _share = SessionShare.tryDecode(text);
     });
   }
 
@@ -45,6 +52,7 @@ class _LoginPageState extends State<LoginPage> {
         _qrController.text = result;
         setState(() {
           _qrCode = SessionModel.extractQRCode(result);
+          _share = SessionShare.tryDecode(result);
         });
         if (mounted) {
           ScaffoldMessenger.of(context).showSnackBar(
@@ -70,44 +78,85 @@ class _LoginPageState extends State<LoginPage> {
   Future<void> _onLogin() async {
     if (_qrCode.isEmpty) return;
 
-    setState(() => _loading = true);
+    if (_qrCode.startsWith("SGWCMAID")) {
+      setState(() => _loading = true);
 
-    try {
-      final result = await SessionModel.instance.loginWithQr(_qrCode);
+      try {
+        final result = await SessionModel.instance.loginWithQr(_qrCode);
 
-      if (!mounted) return;
+        if (!mounted) return;
 
-      if (result.success) {
-        Navigator.of(context).push(
-          MaterialPageRoute(
-            builder: (_) => HomePage(
-              userId: result.userId,
-              token: result.token,
-              forcePreviewApi: _forcePreviewApi,
+        if (result.success) {
+          Navigator.of(context).push(
+            MaterialPageRoute(
+              builder: (_) => HomePage(
+                userId: result.userId,
+                token: result.token,
+                forcePreviewApi: _forcePreviewApi,
+              ),
             ),
-          ),
-        );
-      } else {
-        ScaffoldMessenger.of(context).showSnackBar(
-          SnackBar(content: Text('${AppStrings.loginFailed} (errorID: ${result.errorId})')),
-        );
+          );
+        } else {
+          ScaffoldMessenger.of(context).showSnackBar(
+            SnackBar(
+              content: Text(
+                '${AppStrings.loginFailed} (errorID: ${result.errorId})',
+              ),
+            ),
+          );
+        }
+      } catch (e) {
+        if (mounted) {
+          ScaffoldMessenger.of(context).showSnackBar(
+            SnackBar(content: Text('${AppStrings.requestFailed}: $e')),
+          );
+        }
+      } finally {
+        if (mounted) {
+          setState(() => _loading = false);
+        }
       }
+    }
+  }
+
+  /// 实验性：用主页导出的连接信息恢复会话。带可用 JSESSIONID 就直接续上那次登录，
+  /// 否则退回用令牌重新登录。
+  Future<void> _onRestoreSession() async {
+    final share = _share;
+    if (share == null) return;
+
+    setState(() => _loading = true);
+    try {
+      final result = await SessionModel.instance.restoreFromShare(share);
+      if (!mounted) return;
+      context.showSnack(
+        result.reusedCookie
+            ? AppStrings.sessionRestoreCookie
+            : AppStrings.sessionRestoreToken,
+      );
+      Navigator.of(context).push(
+        MaterialPageRoute(
+          builder: (_) => HomePage(
+            userId: share.userId,
+            token: share.token,
+            sessionRestored: true,
+            initialUserData: result.userData,
+          ),
+        ),
+      );
     } catch (e) {
       if (mounted) {
-        ScaffoldMessenger.of(context).showSnackBar(
-          SnackBar(content: Text('${AppStrings.requestFailed}: $e')),
-        );
+        context.showSnack('${AppStrings.sessionRestoreFailed}: $e');
       }
     } finally {
-      if (mounted) {
-        setState(() => _loading = false);
-      }
+      if (mounted) setState(() => _loading = false);
     }
   }
 
   @override
   Widget build(BuildContext context) {
     final theme = Theme.of(context);
+    final isRestore = _share != null;
 
     return Scaffold(
       appBar: AppBar(
@@ -117,9 +166,9 @@ class _LoginPageState extends State<LoginPage> {
             icon: const Icon(Icons.settings),
             tooltip: AppStrings.settingsTooltip,
             onPressed: () {
-              Navigator.of(context).push(
-                MaterialPageRoute(builder: (_) => const SettingsPage()),
-              );
+              Navigator.of(
+                context,
+              ).push(MaterialPageRoute(builder: (_) => const SettingsPage()));
             },
           ),
         ],
@@ -145,14 +194,7 @@ class _LoginPageState extends State<LoginPage> {
                     color: theme.colorScheme.primary,
                   ),
                 ),
-                const SizedBox(height: 8),
-                Text(
-                  AppStrings.loginSubtitle,
-                  style: theme.textTheme.bodyMedium?.copyWith(
-                    color: theme.colorScheme.onSurfaceVariant,
-                  ),
-                ),
-                const SizedBox(height: 40),
+                const SizedBox(height: 48),
 
                 Card(
                   elevation: 0,
@@ -194,6 +236,7 @@ class _LoginPageState extends State<LoginPage> {
                             letterSpacing: 0.5,
                           ),
                           decoration: InputDecoration(
+                            hintText: AppStrings.qrHint,
                             border: OutlineInputBorder(
                               borderRadius: BorderRadius.circular(10),
                             ),
@@ -205,40 +248,14 @@ class _LoginPageState extends State<LoginPage> {
                   ),
                 ),
 
-                if (_qrCode.isNotEmpty) ...[
-                  const SizedBox(height: 12),
-                  Container(
-                    width: double.infinity,
-                    padding: const EdgeInsets.all(12),
-                    decoration: BoxDecoration(
-                      color: theme.colorScheme.surfaceContainerHighest
-                          .withValues(alpha: 0.5),
-                      borderRadius: BorderRadius.circular(10),
-                    ),
-                    child: Column(
-                      crossAxisAlignment: CrossAxisAlignment.start,
-                      children: [
-                        Text(
-                          AppStrings.qrParsedResult,
-                          style: theme.textTheme.labelSmall?.copyWith(
-                            color: theme.colorScheme.onSurfaceVariant,
-                          ),
-                        ),
-                        const SizedBox(height: 6),
-                        Text(
-                          _qrCode,
-                          style: theme.textTheme.bodySmall?.copyWith(
-                            fontFamily: 'monospace',
-                            color: theme.colorScheme.onSurface,
-                          ),
-                        ),
-                      ],
-                    ),
-                  ),
-                ],
-
                 const SizedBox(height: 28),
 
+                if (isRestore)
+                  const AppNotice(
+                    AppStrings.sessionShareDetected,
+                    icon: Icons.science_outlined,
+                  ),
+
                 Row(
                   children: [
                     Expanded(
@@ -257,8 +274,11 @@ class _LoginPageState extends State<LoginPage> {
                     const SizedBox(width: 16),
                     Expanded(
                       child: FilledButton.icon(
-                        onPressed:
-                            (_qrCode.isNotEmpty && !_loading) ? _onLogin : null,
+                        onPressed: isRestore
+                            ? (_loading ? null : _onRestoreSession)
+                            : (_qrCode.isNotEmpty && !_loading)
+                            ? _onLogin
+                            : null,
                         icon: _loading
                             ? const SizedBox(
                                 width: 20,
@@ -268,8 +288,19 @@ class _LoginPageState extends State<LoginPage> {
                                   color: Colors.white,
                                 ),
                               )
-                            : const Icon(Icons.arrow_forward, size: 20),
-                        label: Text(_loading ? AppStrings.loggingIn : AppStrings.login),
+                            : Icon(
+                                isRestore ? Icons.link : Icons.arrow_forward,
+                                size: 20,
+                              ),
+                        label: Text(
+                          isRestore
+                              ? (_loading
+                                    ? AppStrings.restoringSession
+                                    : AppStrings.restoreSession)
+                              : (_loading
+                                    ? AppStrings.loggingIn
+                                    : AppStrings.login),
+                        ),
                         style: FilledButton.styleFrom(
                           padding: const EdgeInsets.symmetric(vertical: 14),
                           shape: RoundedRectangleBorder(
@@ -281,14 +312,16 @@ class _LoginPageState extends State<LoginPage> {
                   ],
                 ),
                 const SizedBox(height: 16),
-                CheckboxListTile(
-                  value: _forcePreviewApi,
-                  onChanged: (v) => setState(() => _forcePreviewApi = v ?? false),
-                  title: const Text(AppStrings.forcePreviewApi),
-                  controlAffinity: ListTileControlAffinity.leading,
-                  contentPadding: EdgeInsets.zero,
-                  dense: true,
-                ),
+                if (!isRestore)
+                  CheckboxListTile(
+                    value: _forcePreviewApi,
+                    onChanged: (v) =>
+                        setState(() => _forcePreviewApi = v ?? false),
+                    title: const Text(AppStrings.forcePreviewApi),
+                    controlAffinity: ListTileControlAffinity.leading,
+                    contentPadding: EdgeInsets.zero,
+                    dense: true,
+                  ),
               ],
             ),
           ),