feat(lesson-preparation): 备课模块审计重构 — 跨模块解耦 + i18n + 纯函数抽取 + 错误边界

P0-1 跨模块直查修复：publish-service 不再直查 examQuestions 表，新增 exams/data-access.addExamQuestions 接口，复用 classes/data-access.getStudentIdsByClassIds

P0-2 i18n 接入：新增 zh-CN/en 翻译文件，注册 lessonPreparation 命名空间，17 个组件改造为 useTranslations/getTranslations

P1 纯函数抽取：lib/document-migration.ts（类型守卫替代 as 断言）、lib/node-summary.ts（翻译函数注入）、lib/rf-mappers.ts

P1 错误边界+骨架屏：新增 LessonPlanErrorBoundary 和 4 个 Skeleton 组件

P1 Block 注册表：新增 config/block-registry.tsx（BlockRenderer 组件），node-edit-panel 重构为配置驱动渲染

P1 其他修复：exercise-block 改用 router.refresh()，node-editor/lesson-node 复用 lib/ 纯函数

架构图同步：更新 004 和 005 文档

Refs: docs/architecture/audit/lesson-preparation-audit-report.md

src/modules/lesson-preparation/data-access.ts

@@ -16,78 +16,20 @@ import {
 } from "@/shared/db/schema";
 import type { DataScope } from "@/shared/types/permissions";
 import { SYSTEM_TEMPLATES } from "./constants";
+import {
+  migrateV1ToV2,
+  normalizeDocument,
+  buildInitialContent,
+} from "./lib/document-migration";
 import type {
   LessonPlan,
   LessonPlanDocument,
-  LessonPlanDocumentV1,
-  LessonPlanEdge,
   LessonPlanListItem,
-  LessonPlanNode,
   LessonPlanTemplate,
-  TemplateBlockSkeleton,
 } from "./types";
 
-// ---- v1 → v2 迁移：将旧 blocks 数组转换为 nodes + 线性 edges ----
-export function migrateV1ToV2(doc: LessonPlanDocumentV1): LessonPlanDocument {
-  const nodes: LessonPlanNode[] = doc.blocks.map((b, i) => ({
-    ...b,
-    position: { x: 80 + (i % 4) * 280, y: 80 + Math.floor(i / 4) * 200 },
-  }));
-  const edges: LessonPlanEdge[] = [];
-  for (let i = 0; i < nodes.length - 1; i++) {
-    edges.push({
-      id: `e_${nodes[i].id}_${nodes[i + 1].id}`,
-      source: nodes[i].id,
-      target: nodes[i + 1].id,
-    });
-  }
-  return { version: 2, nodes, edges };
-}
-
-// ---- 规范化：确保 content 是 v2 格式（兼容旧数据）----
-export function normalizeDocument(
-  content: unknown,
-): LessonPlanDocument {
-  if (content && typeof content === "object") {
-    const c = content as { version?: number };
-    if (c.version === 2) {
-      return content as LessonPlanDocument;
-    }
-    if (c.version === 1) {
-      return migrateV1ToV2(content as LessonPlanDocumentV1);
-    }
-  }
-  // 空文档
-  return { version: 2, nodes: [], edges: [] };
-}
-
-// ---- 模板初始化：根据骨架生成初始 content（v2）----
-export function buildInitialContent(
-  blocks: TemplateBlockSkeleton[],
-): LessonPlanDocument {
-  const nodes: LessonPlanNode[] = blocks.map((b, i) => ({
-    id: createId(),
-    type: b.type,
-    title: b.title,
-    data:
-      b.type === "exercise"
-        ? { items: [], purpose: "class_practice", knowledgePointIds: [] }
-        : b.type === "text_study"
-          ? { sourceText: "", annotations: [], knowledgePointIds: [] }
-          : { html: "", knowledgePointIds: [] },
-    order: i,
-    position: { x: 80 + (i % 4) * 280, y: 80 + Math.floor(i / 4) * 200 },
-  }));
-  const edges: LessonPlanEdge[] = [];
-  for (let i = 0; i < nodes.length - 1; i++) {
-    edges.push({
-      id: `e_${nodes[i].id}_${nodes[i + 1].id}`,
-      source: nodes[i].id,
-      target: nodes[i + 1].id,
-    });
-  }
-  return { version: 2, nodes, edges };
-}
+// re-export 纯函数保持向后兼容
+export { migrateV1ToV2, normalizeDocument, buildInitialContent };
 
 // ---- DataScope → 查询条件 ----
 function buildScopeCondition(scope: DataScope, userId: string): SQL[] {