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/modules/exams/ai-pipeline/index.ts

@@ -0,0 +1,172 @@
+/**
+ * AI 试卷生成管线（入口模块）
+ *
+ * 本目录由三个子模块组成：
+ * - parse.ts: Zod schema、JSON 解析、纯转换函数、提示词
+ * - request.ts: AI 请求构造与发送
+ * - structure.ts: 结构生成与预览/草稿转换
+ *
+ * 本文件负责：
+ * - 重新导出公共 API（schema、类型、函数）
+ * - 编排高层流程（generateAiPreviewData / generateAiCreateDraftFromSource）
+ */
+
+import { z } from "zod"
+
+import {
+  AiExamResponseSchema,
+  AiQuestionSchema,
+} from "./parse"
+import {
+  parseQuestionDetail,
+  requestAiExamDraft,
+  requestAiExamStructureDraft,
+  validateExamSourceText,
+  type SplitQuestionItem,
+} from "./request"
+import {
+  buildPreviewPayload,
+  mapWithConcurrency,
+  previewToDraft,
+  splitStructureItems,
+} from "./structure"
+
+// ---------------------------------------------------------------------------
+// Re-export public schemas & types
+// ---------------------------------------------------------------------------
+
+export {
+  AiGeneratedStructureSchema,
+  AiGeneratedStructureNodeSchema,
+  AiInsertQuestionSchema,
+  AiQuestionSchema,
+} from "./parse"
+
+export type {
+  AiGeneratedQuestion,
+  AiGeneratedStructureNode,
+  AiPreviewData,
+  AiPreviewQuestion,
+  AiRewriteQuestionData,
+  QuestionContentResult,
+} from "./parse"
+
+// ---------------------------------------------------------------------------
+// Re-export public functions
+// ---------------------------------------------------------------------------
+
+export { regenerateAiQuestionByInstruction } from "./request"
+
+// ---------------------------------------------------------------------------
+// High-level orchestration
+// ---------------------------------------------------------------------------
+
+export async function generateAiPreviewData(input: {
+  title: string
+  subject?: string
+  grade?: string
+  difficulty: number
+  totalScore: number
+  durationMin: number
+  questionCount?: number
+  sourceText: string
+  aiProviderId?: string
+}) {
+  const sourceValidation = await validateExamSourceText({
+    sourceText: input.sourceText,
+    aiProviderId: input.aiProviderId,
+  })
+  if (!sourceValidation.ok) {
+    return { ok: false as const, message: sourceValidation.message }
+  }
+  const structureDraft = await requestAiExamStructureDraft(input)
+  if (!structureDraft.ok) return structureDraft
+  const splitItems = splitStructureItems(structureDraft.data)
+  const limitedItems = typeof input.questionCount === "number" && input.questionCount > 0
+    ? splitItems.slice(0, input.questionCount)
+    : splitItems
+  if (limitedItems.length === 0) {
+    return { ok: false as const, message: "AI returned no questions" }
+  }
+  const detailedQuestions = await mapWithConcurrency(limitedItems, 6, (item) => parseQuestionDetail({
+    item,
+    subject: input.subject,
+    grade: input.grade,
+    difficulty: input.difficulty,
+    aiProviderId: input.aiProviderId,
+  }))
+  const hasSectionStructure = limitedItems.some((item: SplitQuestionItem) => item.sectionIndex !== null)
+  const aiParsed: z.infer<typeof AiExamResponseSchema> = hasSectionStructure
+    ? {
+      title: structureDraft.data.title ?? input.title,
+      sections: (() => {
+        const sectionMap = new Map<number, { title: string; questions: z.infer<typeof AiQuestionSchema>[] }>()
+        limitedItems.forEach((item, index) => {
+          if (item.sectionIndex === null) return
+          const existed = sectionMap.get(item.sectionIndex)
+          const question = detailedQuestions[index]
+          if (existed) {
+            existed.questions.push(question)
+            return
+          }
+          sectionMap.set(item.sectionIndex, {
+            title: item.sectionTitle || `Section ${item.sectionIndex + 1}`,
+            questions: [question],
+          })
+        })
+        return Array.from(sectionMap.entries())
+          .sort((a, b) => a[0] - b[0])
+          .map(([, section]) => section)
+      })(),
+      questions: undefined,
+    }
+    : {
+      title: structureDraft.data.title ?? input.title,
+      questions: detailedQuestions,
+      sections: undefined,
+    }
+  const payload = buildPreviewPayload(aiParsed, input)
+  return {
+    ok: true as const,
+    data: payload,
+    rawOutput: structureDraft.rawOutput,
+  }
+}
+
+export async function generateAiCreateDraftFromSource(input: {
+  title: string
+  subject?: string
+  grade?: string
+  difficulty: number
+  totalScore: number
+  durationMin: number
+  questionCount?: number
+  sourceText: string
+  aiProviderId?: string
+}) {
+  const preview = await generateAiPreviewData(input)
+  if (!preview.ok) {
+    return preview
+  }
+  const draft = previewToDraft(preview.data)
+  return {
+    ok: true as const,
+    generated: draft.generated,
+    structure: draft.structure,
+    rawOutput: preview.rawOutput,
+  }
+}
+
+export async function generateAiExamDraft(input: {
+  title?: string
+  subject?: string
+  grade?: string
+  difficulty?: number
+  totalScore?: number
+  durationMin?: number
+  questionCount?: number
+  sourceText: string
+  aiProviderId?: string
+}) {
+  return requestAiExamDraft(input)
+}