feat：简单添加管理员后台功能

client/src/app/App.tsx

@@ -0,0 +1,26 @@
+import { ConfigProvider } from 'antd';
+import { BrowserRouter, Navigate, Route, Routes } from 'react-router-dom';
+import { AdminLayout } from './AdminLayout';
+import { LoginPage } from '../pages/LoginPage';
+import { UsersPage } from '../pages/UsersPage';
+import { isAuthed } from '../lib/adminAuth';
+
+export function App() {
+  return (
+    <ConfigProvider>
+      <BrowserRouter>
+        <Routes>
+          <Route path="/login" element={<LoginPage />} />
+          <Route
+            path="/"
+            element={isAuthed() ? <AdminLayout /> : <Navigate to="/login" replace />}
+          >
+            <Route index element={<Navigate to="/users" replace />} />
+            <Route path="users" element={<UsersPage />} />
+          </Route>
+          <Route path="*" element={<Navigate to={isAuthed() ? '/users' : '/login'} replace />} />
+        </Routes>
+      </BrowserRouter>
+    </ConfigProvider>
+  );
+}