refactor(attendance,elective): 审计第二轮 — 全量完成 P0/P1 改进项

P0 修复：
- 页面层 i18n 全量补齐（admin/teacher/parent/student × attendance/elective）
- types.ts 状态标签常量迁移至 constants.ts（i18n key + Badge variant）
- 修复 getTranslations 导入路径（next-intl → next-intl/server）

P1 改进：
- 解耦 parent 模块对 attendance 类型的直接依赖（本地 view-model 类型）
- 导出纯函数（computeStats/buildWarnings/buildLotteryRankCase 等）
- 统一空状态为 EmptyState 组件
- 清理死代码读 Action（attendance 5 个 + elective 3 个）
- 预留监控埋点接口（trackEvent 13 个新事件名）
- 补齐骨架屏 loading.tsx（8 个页面）
- AlertDialog 替换 window.confirm（student-selection-view）
- a11y 改进（aria-label/role/键盘导航）

修复：
- AttendanceStatus 从 constants.ts 重导出，消除 types/constants 双源混乱
- buildWarnings 的 Translator 类型改用 ReturnType<typeof useTranslations>

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

@@ -1,7 +1,8 @@
-import Link from "next/link"
+import Link from "next/link"
 import type { Metadata } from "next"
 import type { JSX } from "react"
 import { BarChart3, ClipboardList } from "lucide-react"
+import { getTranslations } from "next-intl/server"
 
 import { Button } from "@/shared/components/ui/button"
 import { EmptyState } from "@/shared/components/ui/empty-state"
@@ -15,11 +16,6 @@ import { AttendanceStatsCards } from "@/modules/attendance/components/attendance
 import { AttendanceRecordList } from "@/modules/attendance/components/attendance-record-list"
 import type { AttendanceStatus } from "@/modules/attendance/types"
 
-export const metadata: Metadata = {
-  title: "考勤总览 - Next_Edu",
-  description: "查看全校所有班级的考勤记录",
-}
-
 export const dynamic = "force-dynamic"
 
 const isValidAttendanceStatus = (v?: string): v is AttendanceStatus =>
@@ -33,6 +29,7 @@ export default async function AdminAttendancePage({
   await requirePermission(Permissions.ATTENDANCE_READ)
   const sp = await searchParams
   const ctx = await getAuthContext()
+  const t = await getTranslations("attendance")
 
   const classId = getSearchParam(sp, "classId")
   const statusParam = getSearchParam(sp, "status")
@@ -62,13 +59,13 @@ export default async function AdminAttendancePage({
     <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">
         <div>
-          <h2 className="text-2xl font-bold tracking-tight">考勤总览</h2>
-          <p className="text-muted-foreground">查看全校所有班级的考勤记录。</p>
+          <h2 className="text-2xl font-bold tracking-tight">{t("title.adminOverview")}</h2>
+          <p className="text-muted-foreground">{t("description.adminOverview")}</p>
         </div>
         <Button asChild variant="outline">
           <Link href="/teacher/attendance/stats">
             <BarChart3 className="mr-2 h-4 w-4" />
-            统计分析
+            {t("actions.stats")}
           </Link>
         </Button>
       </div>
@@ -79,8 +76,8 @@ export default async function AdminAttendancePage({
 
       {result.items.length === 0 && !classId && !status && !date ? (
         <EmptyState
-          title="暂无考勤记录"
-          description="系统中尚未产生任何考勤记录。"
+          title={t("list.empty")}
+          description={t("list.emptyDescription")}
           icon={ClipboardList}
         />
       ) : (