feat(ai): 新增 AI 模块并集成至备课/错题集/试卷/改题四大业务场景

- 新增 src/modules/ai 独立模块，遵循三层架构（actions → services → shared/lib/ai）
- 通过 AiClientProvider + useAiClient 实现 React Context 依赖注入，业务组件零直接 import
- 6 个 Server Actions 均调用 requirePermission() 权限校验，返回 ActionState<T>
- withAiTracking 统一埋点，覆盖 chat/similar_question/grading_assist/lesson_content/question_variant/weakness_analysis
- 集成场景：作业批改 AiGradingAssist、错题集 AiErrorBookAnalysis、备课 AiLessonContentGenerator、试卷 AiQuestionVariantGenerator
- 全量 i18n（en/zh-CN ai.json），Error Boundary + Skeleton 边界处理
- 同步架构图 004/005，新增审计报告 ai-module-audit-report.md

src/app/(dashboard)/teacher/exams/[id]/build/page.tsx

@@ -7,13 +7,45 @@ import { normalizeStructure } from "@/modules/exams/utils/normalize-structure"
 import type { Question } from "@/modules/questions/types"
 import type { ExamNode } from "@/modules/exams/components/assembly/selected-question-list"
 import { createId } from "@paralleldrive/cuid2"
+import { requirePermission } from "@/shared/lib/auth-guard"
+import { Permissions } from "@/shared/types/permissions"
+import {
+  AiClientProvider,
+  type AiClientService,
+} from "@/modules/ai/context/ai-client-provider"
+import {
+  aiChatAction,
+  suggestSimilarQuestionsAction,
+  suggestGradingAction,
+  generateLessonContentAction,
+  generateQuestionVariantAction,
+  analyzeWeaknessAction,
+} from "@/modules/ai/actions"
 
 export const dynamic = "force-dynamic"
 
+/**
+ * 构建 AI 客户端服务（Server Action 引用集合）
+ *
+ * 通过 React Context 注入，客户端组件不直接 import actions，
+ * 遵循依赖注入模式，便于测试时替换为 mock。
+ */
+function createAiClientService(): AiClientService {
+  return {
+    chat: aiChatAction,
+    suggestSimilarQuestions: suggestSimilarQuestionsAction,
+    suggestGrading: suggestGradingAction,
+    generateLessonContent: generateLessonContentAction,
+    generateQuestionVariant: generateQuestionVariantAction,
+    analyzeWeakness: analyzeWeaknessAction,
+  }
+}
+
 export default async function BuildExamPage({ params }: { params: Promise<{ id: string }> }): Promise<JSX.Element> {
   const { id } = await params
 
-  const exam = await getExamById(id)
+  const ctx = await requirePermission(Permissions.EXAM_READ)
+  const exam = await getExamById(id, ctx.dataScope)
   if (!exam) return notFound()
 
   // Fetch initial questions for the bank (pagination handled by client)
@@ -69,24 +101,28 @@ export default async function BuildExamPage({ params }: { params: Promise<{ id:
     }))
   }
 
+  const aiClientService = createAiClientService()
+
   return (
-    <div className="flex h-full flex-col space-y-4 p-4">
-      <div>
-        <h1 className="text-2xl font-bold tracking-tight">Build Exam</h1>
-        <p className="text-muted-foreground">Assemble questions for your exam.</p>
+    <AiClientProvider service={aiClientService}>
+      <div className="flex h-full flex-col space-y-4 p-4">
+        <div>
+          <h1 className="text-2xl font-bold tracking-tight">Build Exam</h1>
+          <p className="text-muted-foreground">Assemble questions for your exam.</p>
+        </div>
+        <ExamAssembly
+          examId={exam.id}
+          title={exam.title}
+          subject={exam.subject}
+          grade={exam.grade}
+          difficulty={exam.difficulty}
+          totalScore={exam.totalScore}
+          durationMin={exam.durationMin}
+          initialSelected={initialSelected}
+          initialStructure={initialStructure}
+          questionOptions={questionOptions}
+        />
       </div>
-      <ExamAssembly
-        examId={exam.id}
-        title={exam.title}
-        subject={exam.subject}
-        grade={exam.grade}
-        difficulty={exam.difficulty}
-        totalScore={exam.totalScore}
-        durationMin={exam.durationMin}
-        initialSelected={initialSelected}
-        initialStructure={initialStructure}
-        questionOptions={questionOptions}
-      />
-    </div>
+    </AiClientProvider>
   )
 }