refactor: 新增员工去掉参保城市选择器，城市从社保账户继承

- 前端：参保城市改为只读显示，从选中的社保账户自动继承
- 前端：去掉参保城市下拉选择器和 cities 查询
- 后端：clampSocialInsBase/clampHousingFundBase 改为优先按 accountId
  查年度标准裁剪基数，回退旧配置表
- 后端：createEmployee 传入 socialAccountId/housingAccountId 给 clamp 函数

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

@@ -670,13 +670,6 @@ export function AddEmployeeModal({ onClose, onSubmit, loading, error }: {
   error: any
 }) {
   const todayStr = new Date().toISOString().slice(0, 10)
-  const { data: cities = ['北京'] } = useQuery<string[]>({
-    queryKey: ['social-config-cities'],
-    queryFn: async () => {
-      const res = await socialInsuranceApi.cities() as any
-      return res?.length ? res : ['北京']
-    },
-  })
   const { data: contractTypes = [] } = useQuery<Array<{ value: string; label: string; hasEndDate: boolean }>>({
     queryKey: ['contract-types'],
     queryFn: async () => {
@@ -951,6 +944,7 @@ export function AddEmployeeModal({ onClose, onSubmit, loading, error }: {
       idCardNumber: form.idCardNumber || undefined,
       phone: form.phone || undefined,
       education: form.education || undefined,
+      city: autoAccounts?.socialAccount?.city || form.city || '北京',
       socialInsBase: form.socialInsBase ? parseFloat(form.socialInsBase) : undefined,
       socialInsStartMonth: form.socialInsStartMonth || undefined,
       housingFundBase: form.housingFundBase ? parseFloat(form.housingFundBase) : undefined,
@@ -1040,28 +1034,7 @@ export function AddEmployeeModal({ onClose, onSubmit, loading, error }: {
           </div>
         )}
         <div className="grid grid-cols-4 gap-4">
-          <div><Label>参保城市</Label><Select value={form.city} onChange={async (e) => {
-            const city = e.target.value
-            setForm({ ...form, city })
-            const salary = Number(form.socialInsBase === '' ? form.monthlySalary : form.socialInsBase) || 0
-            const hfBase = Number(form.housingFundBase === '' ? form.monthlySalary : form.housingFundBase) || 0
-            if (salary > 0) {
-              try {
-                const res = await socialInsuranceApi.calculate(salary, city)
-                if (res?.capped || res?.floored) {
-                  setForm((prev: any) => ({ ...prev, socialInsBase: String(res.actualBase) }))
-                }
-              } catch {}
-            }
-            if (hfBase > 0) {
-              try {
-                const res = await socialInsuranceApi.housingCalculate(hfBase, city)
-                if (res?.capped || res?.floored) {
-                  setForm((prev: any) => ({ ...prev, housingFundBase: String(res.actualBase) }))
-                }
-              } catch {}
-            }
-          }}>{cities.map((c) => <option key={c} value={c}>{c}</option>)}</Select></div>
+          <div><Label>参保城市</Label><div className="text-xs text-gray-600 py-1.5">{autoAccounts?.socialAccount?.city || form.city || '—'}</div><div className="text-xs text-gray-400">从社保账户自动继承</div></div>
           <div><Label>学历</Label><Select value={form.education} onChange={(e) => setForm({ ...form, education: e.target.value })}><option value="">未选择</option><option value="博士">博士</option><option value="硕士">硕士</option><option value="本科">本科</option><option value="大专">大专</option><option value="高中">高中</option><option value="其他">其他</option></Select></div>
         </div>
         {/* 社保公积金 */}