feat(admin): 补全 admin 模块核心功能与产品体验优化

修复 v4 报告中的 13 个产品体验问题：新增用户管理列表页和系统设置页，重组导航菜单并补充缺失入口，增加角色切换机制，Dashboard 增加快捷操作和 recharts 趋势图表，考勤增加统计概览，排课增加课表网格视图，统一 Toast 操作反馈，同步更新架构文档

src/app/(dashboard)/admin/attendance/page.tsx

@@ -9,8 +9,9 @@ import { requirePermission, getAuthContext } from "@/shared/lib/auth-guard"
 import { Permissions } from "@/shared/types/permissions"
 import { getSearchParam, type SearchParams } from "@/shared/lib/utils"
 import { getAdminClasses } from "@/modules/classes/data-access"
-import { getAttendanceRecords } from "@/modules/attendance/data-access"
+import { getAttendanceRecords, getAttendanceStats } from "@/modules/attendance/data-access"
 import { AttendanceFilters } from "@/modules/attendance/components/attendance-filters"
+import { AttendanceStatsCards } from "@/modules/attendance/components/attendance-stats-cards"
 import { AttendanceRecordList } from "@/modules/attendance/components/attendance-record-list"
 import type { AttendanceStatus } from "@/modules/attendance/types"
 
@@ -50,6 +51,13 @@ export default async function AdminAttendancePage({
     date: date && date.length > 0 ? date : undefined,
   })
 
+  const stats = await getAttendanceStats({
+    scope: ctx.dataScope,
+    currentUserId: ctx.userId,
+    classId: classId && classId !== "all" ? classId : undefined,
+    date: date && date.length > 0 ? date : undefined,
+  })
+
   return (
     <div className="h-full flex-1 flex-col space-y-8 p-8 md:flex">
       <div className="flex items-center justify-between space-y-2">
@@ -65,6 +73,8 @@ export default async function AdminAttendancePage({
         </Button>
       </div>
 
+      <AttendanceStatsCards stats={stats} />
+
       <AttendanceFilters classes={classOptions} />
 
       {result.items.length === 0 && !classId && !status && !date ? (