fix: HR系统优化批次1 - P0/P1问题修复

P0-3: 修复合同状态判断逻辑，有合同记录但signDate为null时不再误判未签
P0-5: 修复参保城市默认北京问题，导入和预览均改为null
P0-11: 添加全局ErrorBoundary防止白屏，三处布局均包裹
P1-2: 合同附件改为可选，允许先保存再补充上传
P1-7.2: 排班弹窗增加员工搜索（姓名/部门）
P1-8.2: 加班费导入支持Excel(xlsx/xls)格式，兼容中英文列名
P1-9: 社保/公积金基数月度办理支持逐人修改，后端返回recordId

backend/src/routes/roster.routes.ts

@@ -119,6 +119,7 @@ router.get('/', authMiddleware, async (req: AuthRequest, res, next) => {
             endDate: latestContract.endDate,
             contractType: latestContract.contractType,
             hireDate: e.hireDate,
+            hasRecord: true,
           })
         : getContractStatus({
             signDate: null,
@@ -126,6 +127,7 @@ router.get('/', authMiddleware, async (req: AuthRequest, res, next) => {
             endDate: null,
             contractType: 'UNSIGNED',
             hireDate: e.hireDate,
+            hasRecord: false,
           })
       const isResigned = e.terminations.some((t) => t.status === 'COMPLETED' && t.terminationDate <= today)
       const isPreHire = !isResigned && e.hireDate > todayEnd