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/pages/ApprovalCategoryPage.tsx

@@ -13,7 +13,7 @@ import {
 } from '@/components/ui/table';
 import { Select, SelectContent, SelectItem, SelectTrigger, SelectValue } from '@/components/ui/select';
 import { Plus, Search, RefreshCw, Clock, CheckCircle, XCircle, FileText, Loader2, Eye, Check, XIcon, User, ChevronRight, Play } from 'lucide-react';
-import { approvalApi } from '@/services/api';
+import { approvalApi } from '@/api';
 import { toast } from 'sonner';
 
 export interface FormField {

frontend/src/pages/ApprovalWorkflowPage.tsx

@@ -7,7 +7,7 @@ import {
 import { Card, CardContent } from '@/components/ui/card';
 import { Button } from '@/components/ui/button';
 import { toast } from 'sonner';
-import { approvalWorkflowApi, userApi } from '@/services/api';
+import { approvalWorkflowApi, userApi } from '@/api';
 
 /* ------------------------------------------------------------------ */
 /*  Types                                                               */

frontend/src/pages/AuditOperationsTab.tsx

@@ -20,7 +20,7 @@ import {
   Eye,
   X,
 } from 'lucide-react';
-import { auditApi } from '@/services/api';
+import { auditApi } from '@/api';
 import { useConfirm } from '@/components/ui/confirm-dialog';
 import type { OperationLog } from '@/types';
 

frontend/src/pages/HostMonitor.tsx

@@ -3,7 +3,7 @@
 import { useState, useEffect, useMemo } from 'react';
 import { useSearchParams } from 'react-router-dom';
 import { useQueryClient } from '@tanstack/react-query';
-import { agentApi } from '@/services/api';
+import { agentApi } from '@/api';
 import { useHostList, useHostHistory, usePortPolicy } from '@/hooks/api/useHostMonitor';
 import { queryKeys } from '@/hooks/api/queryKeys';
 import { Card, CardContent } from '@/components/ui/card';

frontend/src/pages/LoginLogsTab.tsx

@@ -13,7 +13,7 @@ import {
   TableRow,
 } from '@/components/ui/table';
 import { Search, RefreshCw, LogIn, Monitor, Globe } from 'lucide-react';
-import { loginLogApi } from '@/services/api';
+import { loginLogApi } from '@/api';
 
 interface LoginLog {
   id: number;

frontend/src/pages/MetricsExplorer.tsx

@@ -5,7 +5,7 @@ import { Select, SelectContent, SelectItem, SelectTrigger, SelectValue } from '@
 import { Button } from '@/components/ui/button';
 import { Input } from '@/components/ui/input';
 import { Activity, Search, Filter, BarChart3, Cpu, HardDrive, Network, Database, Plus } from 'lucide-react';
-import { metricsApi } from '@/services/api';
+import { metricsApi } from '@/api';
 
 interface _MetricName {
   name: string;

frontend/src/pages/MiddlewareMonitor.tsx

@@ -3,7 +3,7 @@ import { useState, useEffect, useCallback } from 'react';
 import { Card, CardContent } from '@/components/ui/card';
 import { Badge } from '@/components/ui/badge';
 import { Database, Server, Activity, Loader2, Circle } from 'lucide-react';
-import { metricsApi } from '@/services/api';
+import { metricsApi } from '@/api';
 
 interface TargetInfo {
   id: number;

frontend/src/pages/SNMPMonitor.tsx

@@ -30,7 +30,7 @@ import {
   TableRow,
 } from '@/components/ui/table';
 import { Radio, Router, HardDrive, Plus, Trash2 } from 'lucide-react';
-import { snmpApi } from '@/services/api';
+import { snmpApi } from '@/api';
 
 // ---------- types ----------
 interface SnmpStats {

frontend/src/pages/SiteMonitor.tsx

@@ -43,7 +43,7 @@ import {
   Activity,
 } from 'lucide-react';
 import { toast } from 'sonner';
-import { siteApi } from '@/services/api';
+import { siteApi } from '@/api';
 import { useConfirm } from '@/components/ui/confirm-dialog';
 
 // 拨测协议类型（与后端 model 对齐：http, https, tcp, dns, ping）

frontend/src/pages/TerminalAuditTab.tsx

@@ -25,7 +25,7 @@ import {
   Timer,
   TimerOff,
 } from 'lucide-react';
-import { terminalSessionApi, sessionCommandApi } from '@/services/api';
+import { terminalSessionApi, sessionCommandApi } from '@/api';
 import { useConfirm } from '@/components/ui/confirm-dialog';
 import { ReplayDialog } from '@/components/system/ReplayDialog';
 import { LiveMonitorDialog } from '@/components/system/LiveMonitorDialog';

frontend/src/pages/host-monitor/HealthProbeSection.tsx

@@ -1,7 +1,7 @@
 // 健康探针 Tab + 对话框 // Logan.Li
 import { useState } from 'react';
 import { useQueryClient } from '@tanstack/react-query';
-import { agentApi } from '@/services/api';
+import { agentApi } from '@/api';
 import { useHealthProbes } from '@/hooks/api/useHostMonitor';
 import { queryKeys } from '@/hooks/api/queryKeys';
 import { Card, CardContent } from '@/components/ui/card';