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

frontend/src/App.tsx

@@ -8,6 +8,7 @@ import MobileTabBar from './components/layout/MobileTabBar'
 import PortalLayout from './components/layout/PortalLayout'
 import PageContainer from './components/layout/PageContainer'
 import { SkeletonPage } from './components/ui/Skeleton'
+import ErrorBoundary from './components/ui/ErrorBoundary'
 
 const Login = lazy(() => import('./pages/auth/Login'))
 const Register = lazy(() => import('./pages/auth/Register'))
@@ -68,7 +69,9 @@ function AdminLayout({ children }: { children: React.ReactNode }) {
         <TopNav onMenuClick={() => setSidebarOpen(true)} />
         <main className="flex-1 py-6 pb-20 md:pb-6">
           <PageContainer>
-            <Suspense fallback={<SkeletonPage />}>{children}</Suspense>
+            <ErrorBoundary>
+              <Suspense fallback={<SkeletonPage />}>{children}</Suspense>
+            </ErrorBoundary>
           </PageContainer>
         </main>
         <MobileTabBar />
@@ -103,7 +106,9 @@ function PlatformLayout({ children }: { children: React.ReactNode }) {
         </header>
         <main className="flex-1 py-6 px-4 md:px-6">
           <div className="max-w-7xl mx-auto">
-            <Suspense fallback={<SkeletonPage />}>{children}</Suspense>
+            <ErrorBoundary>
+              <Suspense fallback={<SkeletonPage />}>{children}</Suspense>
+            </ErrorBoundary>
           </div>
         </main>
       </div>
@@ -116,14 +121,18 @@ function PortalLayoutWrapper({ children, showNav = true }: { children: React.Rea
     return (
       <div className="min-h-screen bg-surface pt-safe pb-safe">
         <main className="max-w-md mx-auto py-6 px-4">
-          <Suspense fallback={<SkeletonPage />}>{children}</Suspense>
+          <ErrorBoundary>
+            <Suspense fallback={<SkeletonPage />}>{children}</Suspense>
+          </ErrorBoundary>
         </main>
       </div>
     )
   }
   return (
     <PortalLayout>
-      <Suspense fallback={<SkeletonPage />}>{children}</Suspense>
+      <ErrorBoundary>
+        <Suspense fallback={<SkeletonPage />}>{children}</Suspense>
+      </ErrorBoundary>
     </PortalLayout>
   )
 }