fix(dashboard): v3 审计修复 — 数据完整性、i18n、类型安全、死代码清理

P0 修复（严重）:
- admin ContentRow 标签与值错配（stats.users→textbooks 等 6 处）
- admin/error.tsx 硬编码中文替换为 useTranslations
- UserGrowthChart 空数据时渲染 EmptyState（userGrowth/homeworkTrend 永远为空数组）

P1 修复（高）:
- 新增 admin/dashboard 和 student/dashboard 的 loading.tsx + error.tsx
- 抽取 DashboardLoadingSkeleton 和 DashboardErrorFallback 共享组件，消除 5 套重复文件
- formatDate/formatLongDate 传入用户 locale（admin/teacher/student 共 6 个组件）
- 移除死代码：getCachedAdminDashboard、AvatarImage src={undefined}、TeacherStats isLoading prop
- filterTodaySchedule 改为泛型函数，消除 as 类型断言
- 辅助函数 getStatus/getDueUrgency 新增显式返回类型
- UserGrowthChart 新增 labelKey prop 区分用户增长/作业提交趋势标签

P2 修复（中）:
- 4 个组件从客户端转为服务端组件（DashboardGreetingHeader、TeacherQuickActions、TeacherDashboardHeader、StudentDashboardHeader）
- Student dashboard 空状态新增 CTA（viewSchedule、viewAll）
- TeacherHomeworkCard 图标按钮新增 aria-label
- TeacherTodoCard 排序逻辑重写为可读的 if/return 模式

同步更新:
- docs/architecture/005_architecture_data.json 新增 DashboardLoadingSkeleton、DashboardErrorFallback 条目
- 新增 docs/architecture/audit/dashboard-audit-report-v3.md 审计报告
- dashboard.json 新增 6 个 i18n 键（textbooks/chapters/questions/exams/totalAssignments/totalSubmissions）

src/shared/lib/track-event.ts

@@ -40,6 +40,24 @@ export type EventName =
   | "elective.course_selected"
   | "elective.course_dropped"
   | "elective.lottery_completed"
+  // 6.7: 考试/作业模块监控事件
+  | "exam.created"
+  | "exam.updated"
+  | "exam.published"
+  | "exam.archived"
+  | "exam.deleted"
+  | "exam.duplicated"
+  | "exam.ai_generated"
+  | "exam.submitted"
+  | "exam.graded"
+  | "homework.created"
+  | "homework.updated"
+  | "homework.published"
+  | "homework.archived"
+  | "homework.deleted"
+  | "homework.submitted"
+  | "homework.graded"
+  | "homework.auto_save_failed"
 
 /** 埋点事件负载 */
 export interface TrackEventPayload {
@@ -90,3 +108,36 @@ export async function trackEvent(payload: TrackEventPayload): Promise<void> {
     // 埋点失败不影响主流程
   }
 }
+
+/**
+ * 6.7: 考试/作业模块专用埋点函数
+ *
+ * 封装 trackEvent，自动设置 targetType，简化调用方代码。
+ *
+ * @example
+ * ```ts
+ * await trackExamEvent("exam.published", { userId: ctx.userId, targetId: examId })
+ * await trackExamEvent("homework.submitted", {
+ *   userId: ctx.userId,
+ *   targetId: submissionId,
+ *   properties: { questionCount, duration: 1200 }
+ * })
+ * ```
+ */
+export async function trackExamEvent(
+  event: Extract<EventName, `exam.${string}` | `homework.${string}`>,
+  params: {
+    userId?: string
+    targetId?: string
+    properties?: Record<string, unknown>
+  }
+): Promise<void> {
+  const targetType = event.startsWith("exam.") ? "exam" : "homework"
+  await trackEvent({
+    event,
+    userId: params.userId,
+    targetId: params.targetId,
+    targetType,
+    properties: params.properties,
+  })
+}