feat: 新增备课模块并修复全模块 P0/P1/P2 缺陷

主要变更:

- 新增 lesson-preparation 模块: 备课编辑器、节点编辑、AI 建议、知识点选择、版本历史、作业发布

- 新增 shared 通用组件: charts/question-bank-filters/schedule-list/ui (chip-nav/filter-bar/page-header/stat-card/stat-item)

- 新增 student/admin 端 loading.tsx 与 error.tsx, 优化加载与错误态体验

- 新增 teacher/lesson-plans 页面 (列表/新建/编辑)

- 新增 drizzle 迁移 0002_tiny_lionheart 及 snapshot

- 新增 textbooks/schema.ts 与 exams/utils/normalize-structure.ts

- 修复 Tiptap v3 SSR hydration 崩溃 (rich-text-block immediatelyRender: false)

- 重构多模块 data-access/actions/组件, 修复权限校验与类型规范

- 同步架构文档 004/005 反映新增模块、导出、依赖关系

- 归档 bugs/* 测试报告与 e2e 测试脚本 (admin/parent/student/teacher web_test)

src/modules/exams/actions.ts

@@ -137,12 +137,24 @@ const loadAiDraftQuestionsAndStructure = async (input: {
     if (!validated.success || validated.data.length === 0) {
       return { ok: false, message: "Invalid AI preview payload" }
     }
-    const generated = validated.data.map((q) => ({
+    const generated: AiGeneratedQuestion[] = validated.data.map((q) => ({
       id: q.id,
       type: q.type,
       difficulty: q.difficulty,
-      content: q.content,
       score: q.score,
+      content: {
+        text: q.content.text,
+        ...(q.content.options
+          ? {
+              options: q.content.options.map((opt) => ({
+                id: opt.id,
+                text: opt.text,
+                isCorrect: opt.isCorrect ?? false,
+              })),
+            }
+          : {}),
+        ...(q.content.subQuestions ? { subQuestions: q.content.subQuestions } : {}),
+      },
     }))
     let structure: AiGeneratedStructureNode[] = []
     if (input.rawStructure) {