refactor: auth expiry - sync JWT exp check, remove async validation

Previous async validateAuth() approach caused: recursion loop,
wrong /me path (404 -> session cleared), init() fetching auth-required
settings without token (cleared session every load).

New synchronous approach:
- Auth.expired(): decodes JWT payload locally, checks exp timestamp
- Auth.logged(): token+user exist AND not expired; auto-clears stale
  session on expiry (no network, no async, no loops)
- route(): simple sync guard - if !Auth.logged() reset + redirect to
  #/login; home page stays public (clears stale cookie only)
- API.req: 401 response -> Auth.reset() + redirect to login unless on
  public page (fallback for server-side revocation/invalid signature)
- Removed validateAuth/_validating/_doRoute entirely

public/js/api.js

@@ -34,6 +34,12 @@ const API = {
     const ct = res.headers.get('content-type');
     if (ct && ct.includes('application/json')) {
       const json = await res.json();
+      if (res.status === 401) {
+        // 服务端判定未登录/过期: 清除本地登录态, 非公开页跳转登录
+        Auth.reset();
+        const page = (location.hash || '#/home').replace('#/', '').split('/')[0];
+        if (!['home', 'login', 'register', 'forgot', 'reset', 'verify', 'install'].includes(page)) location.hash = '#/login';
+      }
       if (!res.ok) throw new Error(json.error || '请求失败');
       return json;
     }

public/js/app.js

@@ -86,28 +86,6 @@ const App = {
   closeModal() { document.getElementById('modal-overlay').classList.add('hidden'); },
   navigate(page, param) { location.hash = `#/${page}` + (param ? `/${param}` : ''); },
 
-  _validating: false,
-
-  // 验证 token 有效性(轻量级,失败则清除登录态)
-  async validateAuth() {
-    if (this._validating) return null; // 防止递归
-    this._validating = true;
-    if (!Auth.logged()) { this._validating = false; return false; }
-    try {
-      await API.get('/auth/me');
-      this._validating = false;
-      return true;
-    } catch (e) {
-      this._validating = false;
-      if (e && e.message && e.message.includes('登录')) {
-        Auth.reset();
-        return false;
-      }
-      // 非登录错误(网络/404/500)不视为登录失效,放行路由
-      return true;
-    }
-  },
-
   route() {
     const hash = location.hash || '#/home';
     const parts = hash.replace('#/', '').split('/');
@@ -123,31 +101,13 @@ const App = {
     if (page === 'home') { this.showPublic('home', param); return; }
     if (page === 'login' || page === 'register' || page === 'forgot' || page === 'reset') { this.showPublic(page); return; }
 
-    // 访问受保护页面前先验证 token 有效性
-    if (Auth.logged() && !this._validating) {
-      this._validating = true; // 标记正在验证
-      this.validateAuth().then(valid => {
-        this._validating = false;
-        if (!valid) {
-          location.hash = '#/login';
-          return;
-        }
-        this._doRoute(page, param);
-      }).catch(() => {
-        this._validating = false;
+    // 受保护页面: Auth.logged() 内部解码 JWT exp,过期自动清除登录态(同步,无异步循环)
+    if (!Auth.logged()) {
       Auth.reset();
       location.hash = '#/login';
-      });
       return;
     }
-    if (!Auth.logged()) {
-      location.hash = '#/login';
-      return;
-    }
-    // 正在验证中,不做任何操作(等待验证完成)
-  },
 
-  _doRoute(page, param) {
     this.showLayout();
     const sidebarPage = (page === 'tickets' && param.startsWith('create')) ? 'tickets-create' : page;
     this.renderSidebar(sidebarPage);

public/js/auth.js

@@ -23,7 +23,25 @@ const Auth = {
 
   token() { return localStorage.getItem(this.TK); },
   user() { try { return JSON.parse(localStorage.getItem(this.US)); } catch { return null; } },
-  logged() { return !!(this.token() && this.user()); },
+
+  // JWT payload 里的 exp(秒) 已过期?
+  expired() {
+    const t = this.token();
+    if (!t) return true;
+    try {
+      let b64 = t.split('.')[1].replace(/-/g, '+').replace(/_/g, '/');
+      b64 = b64.padEnd(b64.length + (4 - b64.length % 4) % 4, '=');
+      const payload = JSON.parse(atob(b64));
+      return payload.exp ? payload.exp * 1000 < Date.now() : false;
+    } catch { return true; }
+  },
+
+  // 登录态判断: token+user 存在 且 未过期;过期自动清除(不跳转)
+  logged() {
+    if (!this.token() || !this.user()) return false;
+    if (this.expired()) { this.reset(); return false; }
+    return true;
+  },
 
   async login(username, password) {
     const d = await API.post('/auth/login', { username, password });