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)/student/attendance/page.tsx

@@ -1,3 +1,4 @@
+import { getTranslations } from "next-intl/server"
 import { getAuthContext } from "@/shared/lib/auth-guard"
 import { getStudentAttendanceSummary } from "@/modules/attendance/data-access-stats"
 import { StudentAttendanceView } from "@/modules/attendance/components/student-attendance-view"
@@ -8,19 +9,20 @@ export const dynamic = "force-dynamic"
 
 export default async function StudentAttendancePage() {
   const ctx = await getAuthContext()
+  const t = await getTranslations("attendance")
 
   const summary = await getStudentAttendanceSummary(ctx.userId)
 
   if (!summary) {
     return (
-      <div className="h-full flex-1 flex-col space-y-8 p-8 md:flex">
+      <div className="space-y-8">
         <div>
-          <h2 className="text-2xl font-bold tracking-tight">My Attendance</h2>
-          <p className="text-muted-foreground">View your attendance records.</p>
+          <h2 className="text-2xl font-bold tracking-tight">{t("title.student")}</h2>
+          <p className="text-muted-foreground">{t("description.student")}</p>
         </div>
         <EmptyState
-          title="No user found"
-          description="Unable to load your student profile."
+          title={t("errors.notFound")}
+          description={t("errors.unexpected")}
           icon={UserX}
           className="border-none shadow-none"
         />
@@ -29,10 +31,10 @@ export default async function StudentAttendancePage() {
   }
 
   return (
-    <div className="h-full flex-1 flex-col space-y-8 p-8 md:flex">
+    <div className="space-y-8">
       <div>
-        <h2 className="text-2xl font-bold tracking-tight">My Attendance</h2>
-        <p className="text-muted-foreground">View your attendance records and statistics.</p>
+        <h2 className="text-2xl font-bold tracking-tight">{t("title.student")}</h2>
+        <p className="text-muted-foreground">{t("description.student")}</p>
       </div>
       <StudentAttendanceView summary={summary} />
     </div>