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/pages/Attendance.tsx

@@ -3,6 +3,7 @@ import { useQuery, useMutation, useQueryClient } from '@tanstack/react-query'
 import { toast } from 'sonner'
 import { CalendarCheck, CheckCircle, Clock, AlertCircle, Plus, Trash2, Calendar, Users, BarChart3, Plane, Upload, Download, X, Send, Loader2, CheckCheck } from 'lucide-react'
 import api from '../lib/api'
+import { employeeApi, rosterApi } from '../lib/api-services'
 import { useAuthStore } from '../store/authStore'
 import Card from '../components/ui/Card'
 import Button from '../components/ui/Button'
@@ -124,10 +125,7 @@ function ConfirmTab() {
 
   const { data: departmentList } = useQuery<string[]>({
     queryKey: ['roster-departments'],
-    queryFn: async () => {
-      const res = await api.get('/roster/departments') as any
-      return res.data || []
-    },
+    queryFn: () => rosterApi.departments(),
   })
 
   const { data: publishRecords } = useQuery<any[]>({
@@ -982,11 +980,8 @@ function LeavesTab() {
   })
 
   const { data: rosterData } = useQuery<any>({
-    queryKey: ['roster-employees'],
-    queryFn: async () => {
-      const res = await api.get('/roster?pageSize=200') as any
-      return res.data
-    },
+    queryKey: ['employee-list'],
+    queryFn: () => employeeApi.list({ status: 'ACTIVE' }),
   })
 
   const createMutation = useMutation({