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/Dashboard.tsx

@@ -0,0 +1,121 @@
+// ============================================================
+// 仪表盘页面
+// ============================================================
+
+import { useQuery } from '@tanstack/react-query'
+import { Card, Col, Row, Statistic, Table, Tag, Typography, Spin, Alert } from 'antd'
+import {
+  TeamOutlined,
+  CloudServerOutlined,
+  ApiOutlined,
+  ThunderboltOutlined,
+  ColumnWidthOutlined,
+} from '@ant-design/icons'
+import { statsService } from '@/services/stats'
+import { logService } from '@/services/logs'
+import type { OperationLog } from '@/types'
+
+const { Title } = Typography
+
+const actionLabels: Record<string, string> = {
+  login: '登录', logout: '登出',
+  create_account: '创建账号', update_account: '更新账号', delete_account: '删除账号',
+  create_provider: '创建服务商', update_provider: '更新服务商', delete_provider: '删除服务商',
+  create_model: '创建模型', update_model: '更新模型', delete_model: '删除模型',
+  create_token: '创建密钥', revoke_token: '撤销密钥',
+  update_config: '更新配置',
+  create_prompt: '创建提示词', update_prompt: '更新提示词', archive_prompt: '归档提示词',
+  desktop_audit: '桌面端审计',
+}
+
+const actionColors: Record<string, string> = {
+  login: 'green', logout: 'default',
+  create_account: 'blue', update_account: 'orange', delete_account: 'red',
+  create_provider: 'blue', update_provider: 'orange', delete_provider: 'red',
+  create_model: 'blue', update_model: 'orange', delete_model: 'red',
+  create_token: 'blue', revoke_token: 'red',
+  update_config: 'orange',
+  create_prompt: 'blue', update_prompt: 'orange', archive_prompt: 'red',
+  desktop_audit: 'default',
+}
+
+export default function Dashboard() {
+  const { data: stats, isLoading: statsLoading, error: statsError } = useQuery({
+    queryKey: ['dashboard-stats'],
+    queryFn: () => statsService.dashboard(),
+  })
+
+  const { data: logsData, isLoading: logsLoading } = useQuery({
+    queryKey: ['recent-logs'],
+    queryFn: () => logService.list({ page: 1, page_size: 10 }),
+  })
+
+  if (statsError) {
+    return <Alert type="error" message="加载仪表盘数据失败" description={(statsError as Error).message} showIcon />
+  }
+
+  const statCards = [
+    { title: '总账号', value: stats?.total_accounts ?? 0, icon: <TeamOutlined />, color: '#1677ff' },
+    { title: '活跃服务商', value: stats?.active_providers ?? 0, icon: <CloudServerOutlined />, color: '#52c41a' },
+    { title: '活跃模型', value: stats?.active_models ?? 0, icon: <ApiOutlined />, color: '#722ed1' },
+    { title: '今日请求', value: stats?.tasks_today ?? 0, icon: <ThunderboltOutlined />, color: '#fa8c16' },
+    { title: '今日 Token', value: ((stats?.tokens_today_input ?? 0) + (stats?.tokens_today_output ?? 0)), icon: <ColumnWidthOutlined />, color: '#eb2f96' },
+  ]
+
+  const logColumns = [
+    {
+      title: '操作类型',
+      dataIndex: 'action',
+      key: 'action',
+      width: 140,
+      render: (action: string) => (
+        <Tag color={actionColors[action] || 'default'}>
+          {actionLabels[action] || action}
+        </Tag>
+      ),
+    },
+    { title: '目标类型', dataIndex: 'target_type', key: 'target_type', width: 100, render: (v: string | null) => v || '-' },
+    {
+      title: '时间',
+      dataIndex: 'created_at',
+      key: 'created_at',
+      width: 180,
+      render: (v: string) => new Date(v).toLocaleString('zh-CN'),
+    },
+  ]
+
+  return (
+    <div>
+      <Title level={4} style={{ marginBottom: 24 }}>仪表盘</Title>
+
+      <Row gutter={[16, 16]} style={{ marginBottom: 24 }}>
+        {statsLoading ? (
+          <Col span={24}><Spin /></Col>
+        ) : (
+          statCards.map((card) => (
+            <Col xs={24} sm={12} md={8} lg={4} key={card.title}>
+              <Card>
+                <Statistic
+                  title={card.title}
+                  value={card.value}
+                  prefix={<span style={{ color: card.color }}>{card.icon}</span>}
+                />
+              </Card>
+            </Col>
+          ))
+        )}
+      </Row>
+
+      <Card title="最近操作日志" size="small">
+        <Table<OperationLog>
+          columns={logColumns}
+          dataSource={logsData?.items ?? []}
+          loading={logsLoading}
+          rowKey="id"
+          pagination={false}
+          size="small"
+        />
+      </Card>
+    </div>
+  )
+}