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/AIAssistant.tsx

@@ -8,6 +8,7 @@ import rehypeRaw from 'rehype-raw'
 import { Document, Packer, Paragraph, HeadingLevel, TextRun, Table, TableRow, TableCell, WidthType, BorderStyle, AlignmentType } from 'docx'
 import { saveAs } from 'file-saver'
 import api from '../lib/api'
+import { employeeApi } from '../lib/api-services'
 import { useAuthStore } from '../store/authStore'
 import Card from '../components/ui/Card'
 import Button from '../components/ui/Button'
@@ -633,11 +634,8 @@ function PredictTab() {
   const [disciplinarySummary, setDisciplinarySummary] = useState('')
 
   const { data: employees } = useQuery<any[]>({
-    queryKey: ['roster-list'],
-    queryFn: async () => {
-      const res = await api.get('/roster?pageSize=999') as any
-      return res.data?.items || res.data || []
-    },
+    queryKey: ['employee-list'],
+    queryFn: () => employeeApi.list({ status: 'ACTIVE' }),
   })
 
   const departments = [...new Set((employees || []).map((e: any) => e.department).filter(Boolean))]
@@ -1384,11 +1382,8 @@ function ReviewTab() {
   }
 
   const { data: employees } = useQuery<any[]>({
-    queryKey: ['roster-list'],
-    queryFn: async () => {
-      const res = await api.get('/roster') as any
-      return res.data?.items || res.data || []
-    },
+    queryKey: ['employee-list'],
+    queryFn: () => employeeApi.list({ status: 'ACTIVE' }),
   })
 
   const handleReview = async () => {
@@ -1580,11 +1575,8 @@ function CaseTab() {
   const { history, saveMutation, deleteMutation, loadHistory } = useAIHistory('case')
 
   const { data: employees } = useQuery<any[]>({
-    queryKey: ['roster-list'],
-    queryFn: async () => {
-      const res = await api.get('/roster') as any
-      return res.data?.items || res.data || []
-    },
+    queryKey: ['employee-list'],
+    queryFn: () => employeeApi.list({ status: 'ACTIVE' }),
   })
 
   const handleMatch = async () => {