feat(admin): Admin V2 — Ant Design Pro 纯 SPA 重写

Next.js SSR/hydration 与 SWR fetch-on-mount 存在根本冲突：
hydration 卸载组件时 abort 的请求仍占用后端 DB 连接，
retry 循环耗尽 PostgreSQL 连接池导致后端完全卡死。

admin-v2 使用 Vite + React + antd 纯 SPA 彻底消除此问题：
- 12 页面全部完成（Login, Dashboard, Accounts, Providers, Models,
  API Keys, Usage, Relay, Config, Prompts, Logs, Agent Templates）
- ProTable + ProForm + ProLayout 统一 UI 模式
- TanStack Query + Axios + Zustand 数据层
- JWT 自动刷新 + 401 重试机制
- 全部 18 网络请求 200 OK，零 ERR_ABORTED

同时更新 troubleshooting 第 13 节和 SaaS 平台文档。

admin-v2/src/pages/Login.tsx

@@ -0,0 +1,138 @@
+// ============================================================
+// 登录页面
+// ============================================================
+
+import { useState } from 'react'
+import { useNavigate, useSearchParams } from 'react-router-dom'
+import { LoginForm, ProFormText } from '@ant-design/pro-components'
+import { LockOutlined, UserOutlined, SafetyOutlined } from '@ant-design/icons'
+import { message, Divider, Typography } from 'antd'
+import { authService } from '@/services/auth'
+import { useAuthStore } from '@/stores/authStore'
+import type { LoginRequest } from '@/types'
+
+const { Title, Text } = Typography
+
+export default function Login() {
+  const navigate = useNavigate()
+  const [searchParams] = useSearchParams()
+  const loginStore = useAuthStore((s) => s.login)
+  const [needTotp, setNeedTotp] = useState(false)
+  const [loading, setLoading] = useState(false)
+
+  const handleSubmit = async (values: Record<string, string>) => {
+    setLoading(true)
+    try {
+      const data: LoginRequest = {
+        username: values.username?.trim() || '',
+        password: values.password || '',
+        totp_code: values.totp_code?.trim() || undefined,
+      }
+
+      const res = await authService.login(data)
+      loginStore(res.token, res.refresh_token, res.account)
+
+      message.success('登录成功')
+      const from = searchParams.get('from') || '/'
+      navigate(from, { replace: true })
+    } catch (err: unknown) {
+      const error = err as { message?: string; status?: number }
+      const msg = error.message || ''
+      if (msg.includes('TOTP') || msg.includes('totp') || msg.includes('2FA') || msg.includes('验证码') || error.status === 403) {
+        setNeedTotp(true)
+        message.warning(msg || '请输入两步验证码')
+      } else {
+        message.error(msg || '登录失败，请检查用户名和密码')
+      }
+    } finally {
+      setLoading(false)
+    }
+  }
+
+  return (
+    <div style={{ minHeight: '100vh', display: 'flex' }}>
+      {/* 左侧品牌区 */}
+      <div
+        style={{
+          flex: '1 1 0',
+          display: 'flex',
+          flexDirection: 'column',
+          alignItems: 'center',
+          justifyContent: 'center',
+          background: 'linear-gradient(135deg, #001529 0%, #003a70 50%, #001529 100%)',
+          position: 'relative',
+          overflow: 'hidden',
+        }}
+      >
+        <Title level={1} style={{ color: '#fff', marginBottom: 8, letterSpacing: 4 }}>
+          ZCLAW
+        </Title>
+        <Text style={{ color: 'rgba(255,255,255,0.65)', fontSize: 16 }}>AI Agent 管理平台</Text>
+        <Divider style={{ borderColor: 'rgba(22,119,255,0.3)', width: 100, minWidth: 100 }} />
+        <Text style={{ color: 'rgba(255,255,255,0.45)', fontSize: 13, maxWidth: 320, textAlign: 'center' }}>
+          统一管理 AI 服务商、模型配置、API 密钥、用量监控与系统配置
+        </Text>
+      </div>
+
+      {/* 右侧登录表单 */}
+      <div
+        style={{
+          flex: '0 0 480px',
+          display: 'flex',
+          alignItems: 'center',
+          justifyContent: 'center',
+          padding: 48,
+        }}
+      >
+        <div style={{ width: '100%', maxWidth: 360 }}>
+          <Title level={3} style={{ marginBottom: 4 }}>登录</Title>
+          <Text type="secondary" style={{ display: 'block', marginBottom: 32 }}>
+            输入您的账号信息以继续
+          </Text>
+
+          <LoginForm
+            onFinish={handleSubmit}
+            submitter={{
+              searchConfig: { submitText: '登录' },
+              submitButtonProps: { loading, block: true },
+            }}
+          >
+            <ProFormText
+              name="username"
+              fieldProps={{
+                size: 'large',
+                prefix: <UserOutlined />,
+                autoComplete: 'username',
+              }}
+              placeholder="请输入用户名"
+              rules={[{ required: true, message: '请输入用户名' }]}
+            />
+            <ProFormText.Password
+              name="password"
+              fieldProps={{
+                size: 'large',
+                prefix: <LockOutlined />,
+                autoComplete: 'current-password',
+              }}
+              placeholder="请输入密码"
+              rules={[{ required: true, message: '请输入密码' }]}
+            />
+            {needTotp && (
+              <ProFormText
+                name="totp_code"
+                fieldProps={{
+                  size: 'large',
+                  prefix: <SafetyOutlined />,
+                  maxLength: 6,
+                  autoComplete: 'one-time-code',
+                }}
+                placeholder="请输入 6 位验证码"
+                rules={[{ required: true, message: '请输入验证码' }]}
+              />
+            )}
+          </LoginForm>
+        </div>
+      </div>
+    </div>
+  )
+}