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/utils/normalize-structure.ts

@@ -0,0 +1,54 @@
+import { createId } from "@paralleldrive/cuid2"
+import type { ExamNode } from "../components/assembly/selected-question-list"
+
+/**
+ * Normalize raw exam structure data into typed `ExamNode[]`.
+ *
+ * - Validates each node's shape at runtime (type guard pattern, no `as`).
+ * - Ensures every node has a unique id (generates one if missing or duplicate).
+ * - Recursively normalizes group children.
+ * - Returns `[]` for non-array input.
+ *
+ * Used by the exam build page to convert persisted `exam.structure` (unknown
+ * JSON from DB) into a typed tree before passing to `<ExamAssembly />`.
+ */
+export function normalizeStructure(nodes: unknown): ExamNode[] {
+  const seen = new Set<string>()
+  const isRecord = (v: unknown): v is Record<string, unknown> =>
+    typeof v === "object" && v !== null
+
+  const normalize = (raw: unknown[]): ExamNode[] => {
+    return raw
+      .map((n): ExamNode | null => {
+        if (!isRecord(n)) return null
+        const type = n.type
+        if (type !== "group" && type !== "question") return null
+
+        let id = typeof n.id === "string" && n.id.length > 0 ? n.id : createId()
+        while (seen.has(id)) id = createId()
+        seen.add(id)
+
+        if (type === "group") {
+          return {
+            id,
+            type: "group",
+            title: typeof n.title === "string" ? n.title : undefined,
+            children: normalize(Array.isArray(n.children) ? n.children : []),
+          } satisfies ExamNode
+        }
+
+        if (typeof n.questionId !== "string" || n.questionId.length === 0) return null
+
+        return {
+          id,
+          type: "question",
+          questionId: n.questionId,
+          score: typeof n.score === "number" ? n.score : undefined,
+        } satisfies ExamNode
+      })
+      .filter((n): n is ExamNode => n !== null)
+  }
+
+  if (!Array.isArray(nodes)) return []
+  return normalize(nodes)
+}