feat: 增强 token 刷新逻辑，添加用户信息恢复功能；优化过期检查处理

Author: ExquisiteCore

frontend/components/Header.tsx

@@ -6,7 +6,7 @@ import Link from 'next/link';
 import ScrollHeader from './ScrollHeader';
 import ThemeToggle from './ThemeToggle';
 import type { User } from '@/types/api';
-import { isTokenExpired, clearAuth, startTokenExpiryWatch, stopTokenExpiryWatch, logout } from '@/lib/auth';
+import { isTokenExpired, startTokenExpiryWatch, stopTokenExpiryWatch, logout } from '@/lib/auth';
 
 // 定义导航菜单项
 const navItems = [

frontend/lib/auth.ts

@@ -126,6 +126,26 @@ async function doRefreshToken(): Promise<string | null> {
     const data = await response.json();
     if (data.token) {
       localStorage.setItem('token', data.token);
+
+      // 如果 user 信息丢失，从 token payload 恢复基本信息
+      if (!localStorage.getItem('user')) {
+        const payload = parseJwtPayload(data.token);
+        if (payload && payload.sub) {
+          const basicUser = {
+            id: payload.sub,
+            username: (payload as { username?: string }).username || '',
+            role: (payload as { role?: string }).role || 'user',
+            email: '',
+            display_name: null,
+            avatar_url: null,
+            bio: null,
+            created_at: '',
+            updated_at: '',
+          };
+          localStorage.setItem('user', JSON.stringify(basicUser));
+        }
+      }
+
       // 触发 storage 事件
       window.dispatchEvent(new StorageEvent('storage', { key: 'token' }));
       return data.token;
@@ -184,19 +204,29 @@ function scheduleNextCheck(): void {
   const timeUntilExpiry = exp - now;
 
   if (timeUntilExpiry <= 0) {
-    // 已过期，立即触发
-    authCheckCallback?.();
+    // 已过期，尝试刷新
+    tryRefreshToken().then((newToken) => {
+      if (!newToken) {
+        clearAuth();
+      }
+      authCheckCallback?.();
+    });
     return;
   }
 
   // 设置定时器，在过期时触发检查
   // 最多等待 60 秒（避免 setTimeout 溢出问题，也保证定期检查）
   const delay = Math.min(timeUntilExpiry, 60) * 1000;
 
-  checkTimer = setTimeout(() => {
+  checkTimer = setTimeout(async () => {
     const currentToken = localStorage.getItem('token');
     if (currentToken && isTokenExpired(currentToken, 0)) {
-      clearAuth();
+      // 尝试刷新而不是直接清除
+      const newToken = await tryRefreshToken();
+      if (!newToken) {
+        // 刷新失败才清除
+        clearAuth();
+      }
       authCheckCallback?.();
     } else {
       // 还没过期，安排下一次检查