refactor: 全量迁移前端 API 调用到统一 api-services 服务层

- 新建 api-services-raw.ts 导出原始 axios 方法供特殊端点使用
- 完成 api-services.ts 全领域覆盖（auth/employee/roster/dashboard/attendance/payroll/socialInsurance/commercialInsurance/termination/policies/evidence/audit/calendar/companyFiles/notifications/settings/ai/platform/portal/survey/search）
- 迁移所有 47+ 页面文件：pages/、pages/roster/、pages/portal/、pages/platform/、pages/auth/、pages/dashboard/、pages/compliance/
- 移除所有直接 import api from '../../lib/api' 引用
- 修复 Termination.tsx / WorkProcess.tsx 中 string|null 类型错误
- 修复 SocialInsurance.tsx 中 api-services-raw delete 导入名
- 修复 PlatformLogin.tsx 变量遮蔽问题
- tsc --noEmit 零错误，vite build 成功

frontend/src/pages/roster/ContractInfo.tsx

@@ -1,7 +1,7 @@
 import { useState, useRef } from "react"
 import { toast } from "sonner"
 import { useQuery, useMutation, useQueryClient } from "@tanstack/react-query"
-import api from "../../lib/api"
+import { employeeApi } from '../../lib/api-services'
 import Card from "../../components/ui/Card"
 import Button from "../../components/ui/Button"
 import { Input, Label, Select } from "../../components/ui/Input"
@@ -17,12 +17,12 @@ export default function ContractInfo({ employeeId, contracts, hireDate }: { empl
   const [previewUrl, setPreviewUrl] = useState<string | null>(null)
 
   const addContractMutation = useMutation({
-    mutationFn: (data: any) => api.post('/employees/contracts', { ...data, employeeId }),
+    mutationFn: (data: any) => employeeApi.addContract({ ...data, employeeId }),
     onSuccess: () => { queryClient.invalidateQueries({ queryKey: ['roster-profile'] }); setShowForm(false) },
   })
 
   const deleteContractMutation = useMutation({
-    mutationFn: (contractId: string) => api.delete(`/employees/contracts/${contractId}`),
+    mutationFn: (contractId: string) => employeeApi.removeContract(contractId),
     onSuccess: () => { queryClient.invalidateQueries({ queryKey: ['roster-profile'] }); toast.success('合同已删除') },
   })