feat: 补充公积金支持（员工级别可选）

上海等城市存在补充公积金账户，同一企业内高管可能有但普通员工
没有。新增员工级别补充公积金账户关联：

- Employee 表加 supplementaryHousingAccountId 字段
- BatchEntry 表加 supplementaryHousingEmp/Org 字段
- 薪资计算 calcBatchEntry 支持补充公积金（额外算一笔，纳入
  个税扣除、最低工资保护递延逻辑）
- 新增员工弹窗加补充公积金账户选择器（可选，仅显示
  accountType=SUPPLEMENTARY 的公积金账户）
- 员工档案编辑支持补充公积金账户

Generated with [Devin](https://devin.ai)

Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

frontend/src/pages/roster/modals.tsx

@@ -732,6 +732,7 @@ export function AddEmployeeModal({ onClose, onSubmit, loading, error }: {
   const [autoAccounts, setAutoAccounts] = useState<{ socialAccount: any; housingAccount: any; socialStandard: any; housingStandard: any } | null>(null)
   const [manualSocialAccountId, setManualSocialAccountId] = useState<string>('')
   const [manualHousingAccountId, setManualHousingAccountId] = useState<string>('')
+  const [supplementaryHousingAccountId, setSupplementaryHousingAccountId] = useState<string>('')
 
   // 部门变化时查询适用账户
   useEffect(() => {
@@ -757,6 +758,8 @@ export function AddEmployeeModal({ onClose, onSubmit, loading, error }: {
     queryFn: () => socialAccountApi.list('HOUSING'),
     enabled: !!form.departmentId,
   })
+  // 补充公积金账户（accountType=SUPPLEMENTARY）
+  const supplementaryHousingAccounts = allHousingAccounts.filter((a: any) => a.accountType === 'SUPPLEMENTARY')
 
   // 入职日期变更 → 同步合同开始日期 + 重算结束日期
   const handleHireDateChange = (hireDate: string) => {
@@ -952,6 +955,7 @@ export function AddEmployeeModal({ onClose, onSubmit, loading, error }: {
       housingFundStartMonth: form.housingFundStartMonth || undefined,
       socialAccountId: manualSocialAccountId || undefined,
       housingAccountId: manualHousingAccountId || undefined,
+      supplementaryHousingAccountId: supplementaryHousingAccountId || undefined,
     }
     if (form.contractType !== 'UNSIGNED' && form.startDate) {
       data.contract = {
@@ -1050,6 +1054,7 @@ export function AddEmployeeModal({ onClose, onSubmit, loading, error }: {
           </div>
           {/* 账户选择（选部门后自动带出，可手动调整） */}
           {!isNoSocialContract && (
+            <>
             <div className="grid grid-cols-2 gap-4 mb-3">
               <div>
                 <Label>社保账户</Label>
@@ -1080,6 +1085,20 @@ export function AddEmployeeModal({ onClose, onSubmit, loading, error }: {
                 )}
               </div>
             </div>
+            {supplementaryHousingAccounts.length > 0 && (
+              <div className="grid grid-cols-2 gap-4 mb-3">
+                <div>
+                  <Label>补充公积金账户（可选）</Label>
+                  <Select value={supplementaryHousingAccountId} onChange={(e) => setSupplementaryHousingAccountId(e.target.value)} disabled={!form.departmentId || isNoSocialContract}>
+                    <option value="">无补充公积金</option>
+                    {supplementaryHousingAccounts.map((a: any) => (
+                      <option key={a.id} value={a.id}>{a.name}（{a.city}）</option>
+                    ))}
+                  </Select>
+                </div>
+              </div>
+            )}
+            </>
           )}
           <div className={`grid grid-cols-4 gap-4 ${isNoSocialContract ? 'opacity-50' : ''}`}>
             <div>