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/modals.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 { rosterApi, socialInsuranceApi } from '../../lib/api-services'
 import Card from "../../components/ui/Card"
 import Button from "../../components/ui/Button"
 import { Input, Label, Select } from "../../components/ui/Input"
@@ -245,8 +245,7 @@ export function RehireModal({ employee, onClose, onSubmit, loading, error }: {
   const { data: contractTypes = [] } = useQuery<Array<{ value: string; label: string; hasEndDate: boolean }>>({
     queryKey: ['contract-types'],
     queryFn: async () => {
-      const res = await api.get('/roster/contract-types') as any
-      return res.data || []
+      return await rosterApi.contractTypes()
     },
     staleTime: Infinity,
   })
@@ -496,15 +495,14 @@ export function AddEmployeeModal({ onClose, onSubmit, loading, error }: {
   const { data: cities = ['北京'] } = useQuery<string[]>({
     queryKey: ['social-config-cities'],
     queryFn: async () => {
-      const res = await api.get('/social/config/cities') as any
-      return res.data?.length ? res.data : ['北京']
+      const res = await socialInsuranceApi.cities() as any
+      return res?.length ? res : ['北京']
     },
   })
   const { data: contractTypes = [] } = useQuery<Array<{ value: string; label: string; hasEndDate: boolean }>>({
     queryKey: ['contract-types'],
     queryFn: async () => {
-      const res = await api.get('/roster/contract-types') as any
-      return res.data || []
+      return await rosterApi.contractTypes()
     },
     staleTime: Infinity,
   })