perf(auth): eliminate login page flicker by moving session check to App.tsx

src/App.tsx

@@ -8,7 +8,7 @@ import GeneratePage from './pages/Generate';
 import ManagePage from './pages/Manage';
 import ProfilePage from './pages/Profile';
 
-const PrivateRoute = () => {
+const PrivatePrivateRoute = () => {
   const user = authApi.getCurrentUser();
   if (!user) {
     return <Navigate to="/login" replace />;
@@ -16,6 +16,14 @@ const PrivateRoute = () => {
   return <Outlet />;
 };
 
+const PublicRoute = ({ children }: { children: React.ReactNode }) => {
+  const user = authApi.getCurrentUser();
+  if (user) {
+    return <Navigate to="/admin/dashboard" replace />;
+  }
+  return <>{children}</>;
+};
+
 const AdminRoutes = () => {
   return (
     <AdminLayout>
@@ -29,7 +37,11 @@ function App() {
     <BrowserRouter>
       <Routes>
         <Route path="/" element={<Navigate to="/login" replace />} />
-        <Route path="/login" element={<LoginPage />} />
+        <Route path="/login" element={
+          <PublicRoute>
+            <LoginPage />
+          </PublicRoute>
+        } />
         <Route path="/query" element={<PublicQueryPage />} />
         
         <Route element={<PrivateRoute />}>

src/pages/Login.tsx

@@ -1,4 +1,4 @@
-import { useState, useEffect } from 'react';
+import { useState } from 'react';
 import { Form, Input, Button, Card, message, Checkbox } from 'antd';
 import { UserOutlined, LockOutlined, LoginOutlined } from '@ant-design/icons';
 import { useNavigate } from 'react-router-dom';
@@ -12,16 +12,6 @@ function LoginPage() {
   const [loading, setLoading] = useState(false);
   const navigate = useNavigate();
 
-  useEffect(() => {
-    const token = localStorage.getItem('authToken');
-    if (token) {
-      const currentUser = authApi.getCurrentUser();
-      if (currentUser) {
-        navigate('/admin/dashboard', { replace: true });
-      }
-    }
-  }, [navigate]);
-
   const handleLogin = async (values: { username: string; password: string; remember?: boolean }) => {
     setLoading(true);
     try {