fix: 劳务协议/实习协议人员薪资计算强制社保公积金为0

calcBatchEntry 查询员工时 include contracts，判断合同类型：
- LABOR（劳务协议）/ INTERNSHIP（实习协议）→ 社保公积金基数强制0，跳过社保计算
- 其他合同类型 → 正常计算

无论哪种批次创建模式（copy_last/blank_employees/custom等），
劳务协议人员的社保公积金都为0。

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

backend/src/services/payroll.service.ts

@@ -206,9 +206,16 @@ export async function calcBatchEntry(
   batchType: string = 'REGULAR',
   options?: { skipSocial?: boolean; overrideSocial?: { socialEmp?: number; socialOrg?: number; housingEmp?: number; housingOrg?: number }; prevDeferred?: { socialEmp?: number; housingEmp?: number; minWage?: number } },
 ) {
-  const employee = await prisma.employee.findFirst({ where: { id: employeeId, orgId } })
+  const employee = await prisma.employee.findFirst({
+    where: { id: employeeId, orgId },
+    include: { contracts: { orderBy: { createdAt: 'desc' }, take: 1 } },
+  })
   if (!employee) throw { code: 'NOT_FOUND', message: '员工不存在' }
 
+  // 劳务协议/实习协议人员：不缴纳社保公积金，基数强制 0
+  const latestContract = employee.contracts[0]
+  const isNoSocialContract = latestContract && ['LABOR', 'INTERNSHIP'].includes(latestContract.contractType)
+
   // 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
@@ -236,15 +243,15 @@ export async function calcBatchEntry(
     })
   }
 
-  // 社保基数：优先用员工核定基数（含0，劳务协议人员基数为0不交社保），未设置时回退到基本工资
+  // 社保基数：劳务协议/实习协议人员强制 0；否则优先用员工核定基数（含0），未设置时回退到基本工资
-  const socialBase = employee.socialInsBase != null ? employee.socialInsBase : inputs.baseSalary
+  const socialBase = isNoSocialContract ? 0 : (employee.socialInsBase != null ? employee.socialInsBase : inputs.baseSalary)
-  const housingBase = employee.housingFundBase != null ? employee.housingFundBase : inputs.baseSalary
+  const housingBase = isNoSocialContract ? 0 : (employee.housingFundBase != null ? employee.housingFundBase : inputs.baseSalary)
 
   let socialEmp = 0, socialOrg = 0, housingEmp = 0, housingOrg = 0
 
-  // 年终奖/奖金批次、补偿金批次：不扣社保公积金
+  // 年终奖/奖金批次、补偿金批次、劳务协议/实习协议人员：不扣社保公积金
   // 其他批次：计算当月应缴全额，减去已归档批次已扣金额，差额为本批次应扣
-  if (batchType !== 'BONUS' && batchType !== 'SEVERANCE' && !options?.skipSocial) {
+  if (batchType !== 'BONUS' && batchType !== 'SEVERANCE' && !options?.skipSocial && !isNoSocialContract) {
     // 1. 计算当月应缴社保公积金全额
     let fullSocialEmp = 0, fullSocialOrg = 0, fullHousingEmp = 0, fullHousingOrg = 0
     if (socialConfig) {