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/pages/Home.tsx

@@ -0,0 +1,37 @@
+import { Typography, Card, Row, Col, Statistic } from 'antd';
+import {
+  UserOutlined,
+  TeamOutlined,
+  FileTextOutlined,
+  BellOutlined,
+} from '@ant-design/icons';
+
+export default function Home() {
+  return (
+    <div>
+      <Typography.Title level={4}>工作台</Typography.Title>
+      <Row gutter={[16, 16]}>
+        <Col xs={24} sm={12} md={6}>
+          <Card>
+            <Statistic title="用户总数" value={0} prefix={<UserOutlined />} />
+          </Card>
+        </Col>
+        <Col xs={24} sm={12} md={6}>
+          <Card>
+            <Statistic title="角色数量" value={0} prefix={<TeamOutlined />} />
+          </Card>
+        </Col>
+        <Col xs={24} sm={12} md={6}>
+          <Card>
+            <Statistic title="流程实例" value={0} prefix={<FileTextOutlined />} />
+          </Card>
+        </Col>
+        <Col xs={24} sm={12} md={6}>
+          <Card>
+            <Statistic title="未读消息" value={0} prefix={<BellOutlined />} />
+          </Card>
+        </Col>
+      </Row>
+    </div>
+  );
+}

apps/web/src/pages/Login.tsx

@@ -0,0 +1,68 @@
+import { useState } from 'react';
+import { useNavigate } from 'react-router-dom';
+import { Form, Input, Button, Card, message, Typography } from 'antd';
+import { UserOutlined, LockOutlined } from '@ant-design/icons';
+import { useAuthStore } from '../stores/auth';
+
+const { Title } = Typography;
+
+export default function Login() {
+  const navigate = useNavigate();
+  const login = useAuthStore((s) => s.login);
+  const loading = useAuthStore((s) => s.loading);
+  const [messageApi, contextHolder] = message.useMessage();
+
+  const onFinish = async (values: { username: string; password: string }) => {
+    try {
+      await login(values.username, values.password);
+      messageApi.success('登录成功');
+      navigate('/');
+    } catch (err: unknown) {
+      const errorMsg =
+        (err as { response?: { data?: { message?: string } } })?.response?.data?.message ||
+        '登录失败，请检查用户名和密码';
+      messageApi.error(errorMsg);
+    }
+  };
+
+  return (
+    <div
+      style={{
+        display: 'flex',
+        justifyContent: 'center',
+        alignItems: 'center',
+        minHeight: '100vh',
+        background: 'linear-gradient(135deg, #667eea 0%, #764ba2 100%)',
+      }}
+    >
+      {contextHolder}
+      <Card style={{ width: 400, borderRadius: 8 }} variant="borderless">
+        <div style={{ textAlign: 'center', marginBottom: 24 }}>
+          <Title level={3} style={{ marginBottom: 4 }}>
+            ERP Platform
+          </Title>
+          <Typography.Text type="secondary">企业资源管理平台</Typography.Text>
+        </div>
+        <Form name="login" onFinish={onFinish} autoComplete="off" size="large">
+          <Form.Item
+            name="username"
+            rules={[{ required: true, message: '请输入用户名' }]}
+          >
+            <Input prefix={<UserOutlined />} placeholder="用户名" />
+          </Form.Item>
+          <Form.Item
+            name="password"
+            rules={[{ required: true, message: '请输入密码' }]}
+          >
+            <Input.Password prefix={<LockOutlined />} placeholder="密码" />
+          </Form.Item>
+          <Form.Item>
+            <Button type="primary" htmlType="submit" loading={loading} block>
+              登录
+            </Button>
+          </Form.Item>
+        </Form>
+      </Card>
+    </div>
+  );
+}