refactor: API口径统一 — 统计函数/员工列表/前端服务层

后端:
- /dashboard/compliance-score 改用 getHealthCheck，与体检诊断同口径
- 新增 /employees/list 端点（不分页，供各页面下拉选择）
- /employees/all-lite 增加 position 字段和 status 筛选参数
- getHealthCheck 未签合同改为查无合同记录的员工（非UNSIGNED类型）

前端:
- 新建 lib/api-services.ts 统一 API 服务层
- employeeApi/rosterApi/dashboardApi/attendanceApi 统一封装
- 6个页面迁移到统一 API 调用:
  - Attendance: employeeApi.list + rosterApi.departments
  - Termination: rosterApi.list + rosterApi.departments
  - Money: rosterApi.list + rosterApi.departments
  - PortalQRModal: employeeApi.list
  - AIAssistant: 3处 employeeApi.list 替代 /roster?pageSize=999
  - Contracts: rosterApi.departments
  - Dashboard: rosterApi.expiringContracts + dashboardApi.healthCheck/workforceStats

frontend/src/components/PortalQRModal.tsx

@@ -7,6 +7,7 @@ import { QRCodeSVG } from 'qrcode.react'
 import { Smartphone, Copy, Check, Search, Loader2, User, ChevronRight } from 'lucide-react'
 import Modal from './ui/Modal'
 import api from '../lib/api'
+import { employeeApi } from '../lib/api-services'
 
 interface Employee {
   id: string
@@ -30,8 +31,7 @@ export default function PortalQRModal({ open, onClose }: { open: boolean; onClos
   useEffect(() => {
     if (!open) return
     setLoading(true)
-    api.get('/roster', { params: { pageSize: 999 } }).then((res: any) => {
-      const list = res.data?.data || res.data || []
+    employeeApi.list({ status: 'ACTIVE' }).then((list: any) => {
       setEmployees(list.map((e: any) => ({
         id: e.id,
         name: e.name,