feat: 预入职状态+入职手续待办

1. 花名册动态状态：hireDate > today 显示「预入职」(蓝色标签)
2. RiskType 增加 ONBOARDING 枚举
3. 新增 detectOnboardingRisks：入职日期到但未签合同→生成待办
4. detectContractRisks 排除预入职员工（未到入职日期不检查合同）
5. Dashboard 风险提醒 tab 支持 ONBOARDING 待办类型
6. 前端类型定义同步更新

frontend/src/pages/Dashboard.tsx

@@ -1,7 +1,7 @@
 import { useState } from 'react'
 import { useQuery, useMutation, useQueryClient } from '@tanstack/react-query'
 import { Link } from 'react-router-dom'
-import { Users, AlertTriangle, CheckSquare, DollarSign, ArrowRight, RefreshCw, FileText, Calendar, TrendingUp, Briefcase, Calculator, Wallet, Building2, Receipt, Check, X, Clock, LayoutDashboard, ListTodo, ShieldAlert } from 'lucide-react'
+import { Users, AlertTriangle, CheckSquare, DollarSign, ArrowRight, RefreshCw, FileText, Calendar, TrendingUp, Briefcase, Calculator, Wallet, Building2, Receipt, Check, X, Clock, LayoutDashboard, ListTodo, ShieldAlert, UserPlus } from 'lucide-react'
 import api from '../lib/api'
 import Card from '../components/ui/Card'
 import Button from '../components/ui/Button'
@@ -18,6 +18,7 @@ const TODO_ICON_CONFIG: Record<string, { icon: typeof FileText; color: string; b
   SALARY: { icon: DollarSign, color: 'text-amber-600', bg: 'bg-amber-50' },
   TERMINATION: { icon: ShieldAlert, color: 'text-red-600', bg: 'bg-red-50' },
   MONTHLY: { icon: Calendar, color: 'text-purple-600', bg: 'bg-purple-50' },
+  ONBOARDING: { icon: UserPlus, color: 'text-cyan-600', bg: 'bg-cyan-50' },
 }
 
 function TodoIcon({ type, level }: { type: string; level: string }) {
@@ -53,7 +54,7 @@ export default function Dashboard() {
     onSuccess: () => queryClient.invalidateQueries({ queryKey: ['dashboard'] }),
   })
 
-  const riskTodos = data?.todos.filter((t) => t.type === 'CONTRACT' || t.type === 'TERMINATION') || []
+  const riskTodos = data?.todos.filter((t) => t.type === 'CONTRACT' || t.type === 'TERMINATION' || t.type === 'ONBOARDING') || []
   const taskTodos = data?.todos.filter((t) => t.type === 'MONTHLY' || t.type === 'SALARY') || []
   const filteredTodos = activeTab === 'risk' ? riskTodos : taskTodos
 

frontend/src/pages/Roster.tsx

@@ -133,8 +133,12 @@ export default function Roster() {
                     <td className="py-2 px-3 font-medium">{e.name}</td>
                     <td className="py-2 px-3 text-gray-500">{e.department}</td>
                     <td className="py-2 px-3">
-                      <span className={`px-2 py-0.5 rounded text-xs ${e.status === 'ACTIVE' ? 'bg-green-50 text-safe' : 'bg-gray-100 text-gray-500'}`}>
-                        {e.status === 'ACTIVE' ? '在职' : '离职'}
+                      <span className={`px-2 py-0.5 rounded text-xs ${
+                        e.status === 'ACTIVE' ? 'bg-green-50 text-safe'
+                        : e.status === 'PRE_HIRE' ? 'bg-blue-50 text-blue-600'
+                        : 'bg-gray-100 text-gray-500'
+                      }`}>
+                        {e.status === 'ACTIVE' ? '在职' : e.status === 'PRE_HIRE' ? '预入职' : '离职'}
                       </span>
                     </td>
                     <td className="py-2 px-3 text-gray-500">{e.hireDate?.toString().slice(0, 10)}</td>

frontend/src/types/index.ts

@@ -85,7 +85,7 @@ export interface DashboardData {
   }
   todos: {
     id: string
-    type: 'CONTRACT' | 'SALARY' | 'TERMINATION' | 'MONTHLY'
+    type: 'CONTRACT' | 'SALARY' | 'TERMINATION' | 'MONTHLY' | 'ONBOARDING'
     level: 'high' | 'medium' | 'low'
     title: string
     description: string
@@ -93,7 +93,7 @@ export interface DashboardData {
   }[]
   resolvedTodos: {
     id: string
-    type: 'CONTRACT' | 'SALARY' | 'TERMINATION' | 'MONTHLY'
+    type: 'CONTRACT' | 'SALARY' | 'TERMINATION' | 'MONTHLY' | 'ONBOARDING'
     level: 'high' | 'medium' | 'low'
     title: string
     description: string