fix: 移除会话失效时强制跳转登录页的行为

前端在检测到 401 或本地无 token 时不再自动跳转到 /login，
改为仅清理本地缓存并抛出错误，由调用方自行决定后续行为。

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

web/src/admin/components/PrivateRoute.tsx

@@ -1,4 +1,3 @@
-import { Navigate } from 'react-router-dom';
 import type { ReactNode } from 'react';
 
 interface PrivateRouteProps {
@@ -13,9 +12,9 @@ const PrivateRoute = ({ children }: PrivateRouteProps) => {
     const token = localStorage.getItem('token');
     const userInfo = localStorage.getItem('userInfo');
 
-    // 如果没有登录信息，重定向到登录页
+    // 如果没有登录信息，返回空占位
     if (!token || !userInfo) {
-        return <Navigate to="/login" replace />;
+        return null;
     }
 
     // 已登录，渲染子组件

web/src/admin/pages/AdminLayout/index.tsx

@@ -90,7 +90,6 @@ const AdminLayout = () => {
         const userInfoStr = localStorage.getItem('userInfo');
 
         if (!token || !userInfoStr) {
-            navigate('/login');
             return;
         }
 

web/src/api/request.ts

@@ -81,7 +81,6 @@ const sendRequest = async <T>(url: string, config: RequestConfig = {}): Promise<
         if (response.status === 401) {
             localStorage.removeItem('token');
             localStorage.removeItem('userInfo');
-            window.location.href = '/login';
             throw new HttpError('未认证或认证已过期', {
                 status: response.status,
                 statusText: response.statusText,