feat: 社保公积金账户化重构

新增 SocialAccount（账户）+ SocialYearStandard（年度标准）两层实体，
替代原 SocialInsuranceConfig/HousingFundConfig 按城市管理的方式。

- DB: 新增 SocialAccount、SocialYearStandard 表，Department 加账户关联
- 迁移: 旧 Config 表数据迁移到 Account + YearStandard
- 后端: 新增账户 CRUD + 年度标准 API，薪资计算适配 accountId
- 前端: 设置页新增账户管理 Tab，组织架构提示 level=0 可关联账户
- 前端: SocialInsurance.tsx 城市选择器改为账户选择器
- 兼容: 旧 Config 表保留，薪资计算回退旧表

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

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

backend/src/services/payroll.service.ts

@@ -1,5 +1,69 @@
 import prisma from '../lib/prisma'
 
+// ========== 社保公积金账户辅助函数 ==========
+
+/**
+ * 通过员工获取适用的社保/公积金账户
+ * 优先从员工所属根部门（level=0）关联的账户继承，回退到公司默认账户
+ */
+async function getEmployeeAccounts(orgId: string, employeeId: string) {
+  const emp = await prisma.employee.findFirst({
+    where: { id: employeeId, orgId },
+    include: { dept: true },
+  })
+  if (!emp) return { socialAccount: null, housingAccount: null }
+
+  // 向上找到 level=0 的根部门
+  let currentDept: any = emp.dept
+  while (currentDept && currentDept.level > 0 && currentDept.parentId) {
+    currentDept = await prisma.department.findUnique({ where: { id: currentDept.parentId } })
+  }
+  const rootDeptId = currentDept?.id || null
+
+  let socialAccount: any = null
+  let housingAccount: any = null
+  if (rootDeptId) {
+    const rootDept = await prisma.department.findUnique({
+      where: { id: rootDeptId },
+      include: { socialAccount: true, housingAccount: true },
+    })
+    socialAccount = rootDept?.socialAccount || null
+    housingAccount = rootDept?.housingAccount || null
+  }
+
+  // 回退到公司默认账户
+  if (!socialAccount) {
+    socialAccount = await prisma.socialAccount.findFirst({ where: { orgId, type: 'SOCIAL', isDefault: true } })
+  }
+  if (!housingAccount) {
+    housingAccount = await prisma.socialAccount.findFirst({ where: { orgId, type: 'HOUSING', isDefault: true } })
+  }
+
+  return { socialAccount, housingAccount }
+}
+
+/**
+ * 通过账户获取指定月份的年度标准
+ */
+async function getStandardByAccountAndMonth(accountId: string, month: string) {
+  const standard = await prisma.socialYearStandard.findFirst({
+    where: {
+      accountId,
+      effectiveFrom: { lte: month },
+      OR: [{ effectiveTo: null }, { effectiveTo: { gte: month } }],
+    },
+    orderBy: { effectiveFrom: 'desc' },
+  })
+  if (!standard) {
+    // 回退到当前生效标准
+    return prisma.socialYearStandard.findFirst({
+      where: { accountId, isCurrent: true },
+      orderBy: { effectiveFrom: 'desc' },
+    })
+  }
+  return standard
+}
+
 // ========== 薪酬模版 ==========
 
 const DEFAULT_ITEMS: { name: string; code: string; type: 'INPUT' | 'CALCULATED'; formula: string | null; order: number; isDefault: boolean; isEditable: boolean }[] = [
@@ -142,25 +206,32 @@ export async function calcBatchEntry(
   const employee = await prisma.employee.findFirst({ where: { id: employeeId, orgId } })
   if (!employee) throw { code: 'NOT_FOUND', message: '员工不存在' }
 
+  // 通过员工账户查年度标准（新逻辑），回退到旧配置（兼容）
+  const { socialAccount, housingAccount } = await getEmployeeAccounts(orgId, employeeId)
+  let socialConfig: any = null
+  let housingConfig: any = null
+
+  if (socialAccount) {
+    socialConfig = await getStandardByAccountAndMonth(socialAccount.id, month)
+  }
+  if (housingAccount) {
+    housingConfig = await getStandardByAccountAndMonth(housingAccount.id, month)
+  }
+
+  // 回退到旧配置表（兼容未迁移数据）
   const cityWhere = employee.city ? { orgId, city: employee.city } : { orgId }
-  const [socialConfig, housingConfig] = await Promise.all([
-    prisma.socialInsuranceConfig.findFirst({
-      where: {
-        ...cityWhere,
-        effectiveFrom: { lte: month },
-        OR: [{ effectiveTo: null }, { effectiveTo: { gte: month } }],
-      },
+  if (!socialConfig) {
+    socialConfig = await prisma.socialInsuranceConfig.findFirst({
+      where: { ...cityWhere, effectiveFrom: { lte: month }, OR: [{ effectiveTo: null }, { effectiveTo: { gte: month } }] },
       orderBy: { effectiveFrom: 'desc' },
-    }),
-    prisma.housingFundConfig.findFirst({
-      where: {
-        ...cityWhere,
-        effectiveFrom: { lte: month },
-        OR: [{ effectiveTo: null }, { effectiveTo: { gte: month } }],
-      },
+    })
+  }
+  if (!housingConfig) {
+    housingConfig = await prisma.housingFundConfig.findFirst({
+      where: { ...cityWhere, effectiveFrom: { lte: month }, OR: [{ effectiveTo: null }, { effectiveTo: { gte: month } }] },
       orderBy: { effectiveFrom: 'desc' },
-    }),
-  ])
+    })
+  }
 
   // 社保基数：优先用员工核定基数，否则用基本工资
   const socialBase = employee.socialInsBase || inputs.baseSalary