feat(web): add login page, auth store, API client, and route guard

- API client with axios interceptors: JWT attach + 401 auto-refresh
- Auth store (Zustand): login/logout/loadFromStorage with localStorage
- Login page: gradient background, Ant Design form, error handling
- Home page: dashboard with statistics cards
- App.tsx: PrivateRoute guard, /login route, auth state restoration
- MainLayout: dynamic user display, logout dropdown, menu navigation
- Users API service: CRUD with pagination support

apps/web/src/App.tsx

@@ -1,29 +1,53 @@
-import { HashRouter, Routes, Route } from 'react-router-dom';
+import { useEffect } from 'react';
+import { HashRouter, Routes, Route, Navigate } from 'react-router-dom';
 import { ConfigProvider, theme as antdTheme } from 'antd';
 import zhCN from 'antd/locale/zh_CN';
 import MainLayout from './layouts/MainLayout';
+import Login from './pages/Login';
+import Home from './pages/Home';
+import { useAuthStore } from './stores/auth';
 import { useAppStore } from './stores/app';
 
-function HomePage() {
-  return <div>欢迎来到 ERP 平台</div>;
+function PrivateRoute({ children }: { children: React.ReactNode }) {
+  const isAuthenticated = useAuthStore((s) => s.isAuthenticated);
+  return isAuthenticated ? <>{children}</> : <Navigate to="/login" replace />;
 }
 
 export default function App() {
-  const { theme: appTheme } = useAppStore();
+  const loadFromStorage = useAuthStore((s) => s.loadFromStorage);
+  const theme = useAppStore((s) => s.theme);
+
+  // Restore auth state from localStorage on app load
+  useEffect(() => {
+    loadFromStorage();
+  }, [loadFromStorage]);
 
   return (
     <ConfigProvider
       locale={zhCN}
       theme={{
-        algorithm: appTheme === 'dark' ? antdTheme.darkAlgorithm : antdTheme.defaultAlgorithm,
+        algorithm: theme === 'dark' ? antdTheme.darkAlgorithm : antdTheme.defaultAlgorithm,
       }}
     >
       <HashRouter>
-        <MainLayout>
-          <Routes>
-            <Route path="/" element={<HomePage />} />
-          </Routes>
-        </MainLayout>
+        <Routes>
+          <Route path="/login" element={<Login />} />
+          <Route
+            path="/"
+            element={
+              <PrivateRoute>
+                <MainLayout>
+                  <Routes>
+                    <Route path="/" element={<Home />} />
+                    <Route path="/users" element={<div>用户管理（开发中）</div>} />
+                    <Route path="/roles" element={<div>权限管理（开发中）</div>} />
+                    <Route path="/settings" element={<div>系统设置（开发中）</div>} />
+                  </Routes>
+                </MainLayout>
+              </PrivateRoute>
+            }
+          />
+        </Routes>
       </HashRouter>
     </ConfigProvider>
   );