feat(client): 实时授权状态与会话失效处理

- 心跳读取 /auth/ping 回带的授权概况，直接刷新横幅/状态栏/只读门禁，省去单独轮询 /license/info
- 账号被停用/删除（401 USER_DISABLED）即强制重新登录
- 令牌持久化经串行队列 + 会话代号守卫，杜绝续期写入与登出交叉把失效 token 写回
- 写操作门禁（write_guard）+ 授权文案（license_copy）按 grace/readonly/locked 分阶段降级

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

client/lib/screens/shell/app_shell.dart

@@ -8,6 +8,7 @@ import 'package:flutter/foundation.dart' show kIsWeb;
 import '../../core/auth/auth_state.dart';
 import '../../widgets/write_guard.dart';
 import '../../core/config/app_config.dart';
+import '../../core/config/license_copy.dart';
 import '../../core/responsive/responsive.dart';
 import '../../core/theme/app_theme.dart';
 import '../../providers/connectivity_provider.dart';
@@ -170,6 +171,14 @@ class _AppShellState extends ConsumerState<AppShell> {
     final user = ref.watch(authStateProvider).user;
     // 登录态心跳：随 shell 挂载存活，~30s 一次，感知被踢下线
     ref.watch(sessionHeartbeatProvider);
+    // 全局轻提示（写请求被后端 403 拒绝等）：统一在此弹出并清空。
+    ref.listen<String?>(apiMessageProvider, (prev, next) {
+      if (next == null || next.isEmpty) return;
+      ScaffoldMessenger.of(context)
+        ..clearSnackBars()
+        ..showSnackBar(SnackBar(content: Text(next)));
+      ref.read(apiMessageProvider.notifier).state = null;
+    });
     final isOnline = ref.watch(connectivityProvider);
     final location = GoRouterState.of(context).matchedLocation;
     final isMobile = context.isMobile;
@@ -538,6 +547,8 @@ class _AppShellState extends ConsumerState<AppShell> {
                                             .valueOrNull ??
                                         'v1.0.0',
                                     iconOnly: iconOnly),
+                                _LicenseStatusItem(
+                                    lic: licenseInfo, iconOnly: iconOnly),
                               ],
                             ),
                           );
@@ -556,19 +567,8 @@ class _AppShellState extends ConsumerState<AppShell> {
   }
 
   Widget _buildLicenseBanner(LicenseInfo lic) {
-    final Color bg;
-    final String msg;
-    switch (lic.phase) {
-      case 'locked':
-        bg = AppTheme.danger;
-        msg = '授权已锁定，所有写操作已停用 — 请立即续费或激活新授权码';
-      case 'readonly':
-        bg = const Color(0xFFB71C1C);
-        msg = '授权已过期，当前为只读模式（剩余宽限期 ${lic.daysRemaining ?? 0} 天后彻底锁定）';
-      default: // grace
-        bg = const Color(0xFFE65100);
-        msg = '授权将于 ${lic.daysRemaining ?? 0} 天后到期，请及时续费';
-    }
+    final bg = LicenseCopy.bannerColor(lic.phase);
+    final msg = LicenseCopy.banner(lic);
     return Container(
       width: double.infinity,
       color: bg,
@@ -584,7 +584,7 @@ class _AppShellState extends ConsumerState<AppShell> {
                 overflow: TextOverflow.ellipsis),
           ),
           TextButton(
-            onPressed: () => context.go('/settings'),
+            onPressed: () => context.go('/settings?tab=license'),
             style: TextButton.styleFrom(foregroundColor: Colors.white70),
             child: const Text('去激活'),
           ),
@@ -594,23 +594,9 @@ class _AppShellState extends ConsumerState<AppShell> {
   }
 
   void _showLicenseExpiryDialog(BuildContext ctx, LicenseInfo lic) {
-    final String title;
-    final String body;
-    final Color titleColor;
-    switch (lic.phase) {
-      case 'locked':
-        title = '授权已锁定';
-        body = '您的授权已到期超过 15 天，所有写操作已停用。\n请前往「设置 → 授权」激活新的授权码，或联系客服续费。';
-        titleColor = AppTheme.danger;
-      case 'readonly':
-        title = '授权已过期 · 只读模式';
-        body = '您的授权已过期，系统进入只读模式，无法执行任何写操作。\n到期 15 天后将彻底锁定登录，请尽快续费。';
-        titleColor = AppTheme.danger;
-      default: // grace
-        title = '授权即将到期';
-        body = '您的授权将在 ${lic.daysRemaining ?? 0} 天后到期，到期后系统进入只读模式。\n请提前联系客服续费，避免影响正常使用。';
-        titleColor = Colors.orange[800]!;
-    }
+    final (title, body) = LicenseCopy.dialog(lic);
+    final Color titleColor =
+        lic.phase == 'grace' ? Colors.orange[800]! : AppTheme.danger;
     showDialog(
       context: ctx,
       barrierDismissible: true,
@@ -630,7 +616,7 @@ class _AppShellState extends ConsumerState<AppShell> {
             style: ElevatedButton.styleFrom(backgroundColor: titleColor),
             onPressed: () {
               Navigator.pop(_);
-              ctx.go('/settings');
+              ctx.go('/settings?tab=license');
             },
             child: const Text('立即前往', style: TextStyle(color: Colors.white)),
           ),
@@ -743,6 +729,43 @@ class _StatusItem extends StatelessWidget {
   }
 }
 
+/// 状态栏「授权到期」项：按到期后时长分三级，用颜色 + 文案区分。
+/// 没到期 → 正常（绿）；过期 ≤7 天（宽限期）→ 警告（橙）；过期 >7 天 → error（红）。
+/// 对应后端 phase：normal / grace / readonly|locked。
+class _LicenseStatusItem extends StatelessWidget {
+  final LicenseInfo? lic;
+  final bool iconOnly;
+  const _LicenseStatusItem({required this.lic, this.iconOnly = false});
+
+  @override
+  Widget build(BuildContext context) {
+    final lic = this.lic;
+    if (lic == null) return const SizedBox.shrink();
+
+    final color = LicenseCopy.phaseColor(lic.phase);
+    final icon = LicenseCopy.phaseIcon(lic.phase);
+
+    final String date = lic.expiresAt == null
+        ? ''
+        : DateFormat('yyyy-MM-dd').format(lic.expiresAt!);
+    final String text = LicenseCopy.statusBar(lic, date);
+
+    return Row(
+      mainAxisSize: MainAxisSize.min,
+      children: [
+        const _StatusDivider(),
+        Icon(icon, size: 11, color: color),
+        if (!iconOnly) ...[
+          const SizedBox(width: 4),
+          Text(text,
+              style: TextStyle(
+                  color: color, fontSize: 11, fontWeight: FontWeight.w600)),
+        ],
+      ],
+    );
+  }
+}
+
 class _StatusDivider extends StatelessWidget {
   const _StatusDivider();
   @override