refactor: 调整侧边栏分组顺序，电子签署移至团队分组

- 电子签署从「福利保障」移到「团队」分组（与合同管理、用工办理同属员工生命周期）
- 「时间」分组移到「薪酬」之前
- 导航顺序：首页 → 团队 → 时间 → 薪酬 → 福利保障 → 合规

frontend/src/components/layout/SidebarNav.tsx

@@ -46,6 +46,14 @@ const navGroups: NavGroup[] = [
       { path: '/work-process', label: '用工办理', icon: ClipboardList },
       { path: '/termination', label: '离职管理', icon: UserX },
       { path: '/special-status', label: '特殊状态', icon: Heart },
+      { path: '/esign', label: '电子签署', icon: PenTool },
+    ],
+  },
+  {
+    title: '时间',
+    items: [
+      { path: '/attendance', label: '考勤排班', icon: CalendarCheck },
+      { path: '/leave-approval', label: '休假审批', icon: CalendarClock },
     ],
   },
   {
@@ -61,14 +69,6 @@ const navGroups: NavGroup[] = [
     items: [
       { path: '/commercial-insurance', label: '商业保险', icon: Umbrella },
       { path: '/benefits', label: '员工福利', icon: Gift },
-      { path: '/esign', label: '电子签署', icon: PenTool },
-    ],
-  },
-  {
-    title: '时间',
-    items: [
-      { path: '/attendance', label: '考勤排班', icon: CalendarCheck },
-      { path: '/leave-approval', label: '休假审批', icon: CalendarClock },
     ],
   },
   {