feat(attendance,elective): 考勤与选修课模块审计重构 — P0 修复 + i18n + Error Boundary

审计报告：docs/architecture/audit/attendance-elective-audit-report.md

P0 修复：
- attendance: getAttendanceStats 统计失真（仅基于前 20 条记录）改为 SQL 聚合查询
- attendance: getClassStudentsForAttendance 跨模块直查 classEnrollments 改为调用 classes data-access
- attendance: update/delete Action 新增资源归属校验（assertRecordOwnership）
- elective: update/delete/openSelection/closeSelection/runLottery Action 新增资源归属校验（assertCourseOwnership）

i18n 接入：
- 新增 attendance/elective 命名空间（zh-CN + en）
- attendance-stats-cards 接入 useTranslations
- elective-course-list/form 接入 useTranslations

类型安全（P1）：
- elective-course-form: 移除 as 断言，改用类型守卫 isSelectionMode
- elective-course-list: 移除 null as never 类型逃逸，改用泛型

Error Boundary：
- 新增 admin/teacher attendance error.tsx
- 新增 admin/student elective error.tsx

架构图同步：
- 004: 修正 attendance/elective/parent 章节的导出函数、文件清单、已知问题
- 005: 修正 actions 的 usedBy（标记无调用方的死代码）、新增 issues 字段、更新依赖矩阵

src/modules/attendance/components/attendance-stats-cards.tsx

@@ -1,4 +1,5 @@
 import { Users, CheckCircle2, XCircle, Clock, LogOut, FileText } from "lucide-react"
+import { useTranslations } from "next-intl"
 
 import { Card, CardContent, CardHeader, CardTitle } from "@/shared/components/ui/card"
 
@@ -15,44 +16,45 @@ interface AttendanceStatsCardsProps {
 }
 
 export function AttendanceStatsCards({ stats }: AttendanceStatsCardsProps) {
+  const t = useTranslations("attendance")
   const cards = [
     {
-      title: "总记录数",
+      title: t("stats.totalRecords"),
       value: stats.totalRecords,
       icon: FileText,
       color: "text-blue-500",
       bgColor: "bg-blue-500/10",
     },
     {
-      title: "出勤",
+      title: t("stats.present"),
       value: stats.presentCount,
       icon: CheckCircle2,
       color: "text-green-500",
       bgColor: "bg-green-500/10",
     },
     {
-      title: "缺勤",
+      title: t("stats.absent"),
       value: stats.absentCount,
       icon: XCircle,
       color: "text-red-500",
       bgColor: "bg-red-500/10",
     },
     {
-      title: "迟到",
+      title: t("stats.late"),
       value: stats.lateCount,
       icon: Clock,
       color: "text-yellow-500",
       bgColor: "bg-yellow-500/10",
     },
     {
-      title: "早退",
+      title: t("stats.earlyLeave"),
       value: stats.earlyLeaveCount,
       icon: LogOut,
       color: "text-orange-500",
       bgColor: "bg-orange-500/10",
     },
     {
-      title: "出勤率",
+      title: t("stats.attendanceRate"),
       value: `${stats.attendanceRate}%`,
       icon: Users,
       color: "text-primary",