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/modules/attendance/constants.ts

@@ -0,0 +1,65 @@
+/**
+ * 考勤模块共享常量（消除 types.ts / attendance-sheet.tsx / attendance-filters.tsx / parent-attendance-calendar.tsx 重复定义）。
+ *
+ * 注意：标签使用 i18n key（`status.*`），由组件层通过 `useTranslations("attendance")` 解析。
+ */
+import type { AttendanceStatus } from "./types"
+
+/** 重导出类型，便于组件层从 constants 单点导入（消除 types/constants 双源混乱） */
+export type { AttendanceStatus } from "./types"
+
+/** 考勤状态选项（顺序即 UI 展示顺序） */
+export const ATTENDANCE_STATUS_OPTIONS: AttendanceStatus[] = [
+  "present",
+  "absent",
+  "late",
+  "early_leave",
+  "excused",
+]
+
+/** 考勤状态 → i18n key 映射（组件层 `t(key)` 解析） */
+export const ATTENDANCE_STATUS_LABEL_KEYS: Record<AttendanceStatus, string> = {
+  present: "status.present",
+  absent: "status.absent",
+  late: "status.late",
+  early_leave: "status.early_leave",
+  excused: "status.excused",
+}
+
+/** 考勤状态 → Badge variant 映射 */
+export const ATTENDANCE_STATUS_BADGE_VARIANTS: Record<AttendanceStatus, "default" | "secondary" | "destructive" | "outline"> = {
+  present: "default",
+  absent: "destructive",
+  late: "secondary",
+  early_leave: "outline",
+  excused: "outline",
+}
+
+/** 考勤状态 → Tailwind 圆点颜色类 */
+export const ATTENDANCE_STATUS_DOT_COLORS: Record<AttendanceStatus, string> = {
+  present: "bg-green-500",
+  absent: "bg-red-500",
+  late: "bg-yellow-500",
+  early_leave: "bg-blue-500",
+  excused: "bg-purple-500",
+}
+
+/** 键盘快捷键映射 */
+export const ATTENDANCE_STATUS_SHORTCUTS: Record<string, AttendanceStatus> = {
+  p: "present",
+  a: "absent",
+  l: "late",
+  e: "early_leave",
+  x: "excused",
+}
+
+/** 初始化状态计数，避免 `{} as Record<...>` 类型断言 */
+export function createInitialStatusCounts(): Record<AttendanceStatus, number> {
+  return {
+    present: 0,
+    absent: 0,
+    late: 0,
+    early_leave: 0,
+    excused: 0,
+  }
+}