refactor(frontend): services/api 迁至 src/api，http 迁至 utils/request

对齐 Vue 后台惯例：
- src/api/          域 API（原 services/api）
- src/utils/request.ts  HTTP 封装（原 services/http.ts）
- src/utils/export.ts  客户端导出工具
- src/utils/index.ts   工具统一出口

全局导入改为 @/api 与 @/utils/request，tsc + build 通过。

frontend/src/components/monitor/dashboard/GrafanaDashboard.tsx

@@ -35,7 +35,7 @@ import { Select, SelectContent, SelectItem, SelectTrigger, SelectValue } from '@
 import { Label } from '@/components/ui/label';
 import { toast } from 'sonner';
 import { useUserStore } from '@/store';
-import { dashboardApi, promDatasourceApi, zabbixDatasourceApi, agentApi, serverApi } from '@/services/api';
+import { dashboardApi, promDatasourceApi, zabbixDatasourceApi, agentApi, serverApi } from '@/api';
 import { GrafanaPanelContent } from './GrafanaPanelContent';
 import { ZabbixDashboard } from './ZabbixDashboard';
 import { PrometheusDashboard } from './PrometheusDashboard';

frontend/src/components/monitor/dashboard/HostMonitorDashboard.tsx

@@ -28,7 +28,7 @@ import { Card, CardContent, CardHeader, CardTitle } from '@/components/ui/card';
 import {
   Select, SelectContent, SelectItem, SelectTrigger, SelectValue
 } from '@/components/ui/select';
-import { serverApi } from '@/services/api';
+import { serverApi } from '@/api';
 
 type SortField = 'hostname' | 'ip' | 'agent_version' | 'agent_status' | 'cpu_usage' | 'memory_usage' | 'disk_usage' | 'region';
 type SortDir = 'asc' | 'desc';

frontend/src/components/monitor/dashboard/PrometheusDashboard.tsx

@@ -6,7 +6,7 @@ import { Badge } from '@/components/ui/badge';
 import { Card, CardContent, CardHeader, CardTitle } from '@/components/ui/card';
 import { StatStrip } from '@/components/ui/stat-strip';
 import { Tabs, TabsContent, TabsList, TabsTrigger } from '@/components/ui/tabs';
-import { prometheusProxyApi } from '@/services/api';
+import { prometheusProxyApi } from '@/api';
 
 interface Props { dsUrl?: string; }
 

frontend/src/components/monitor/dashboard/ZabbixDashboard.tsx

@@ -16,7 +16,7 @@ import {
 import { Button } from '@/components/ui/button';
 import { Badge } from '@/components/ui/badge';
 import { Card, CardContent, CardHeader, CardTitle } from '@/components/ui/card';
-import { zabbixProxyApi } from '@/services/api';
+import { zabbixProxyApi } from '@/api';
 
 interface ZabbixHost {
   hostid: string; hostname: string; name: string; ip: string; available: string;