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/lib/document-migration.ts

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+import { createId } from "@paralleldrive/cuid2";
+import type {
+  LessonPlanDocument,
+  LessonPlanDocumentV1,
+  LessonPlanEdge,
+  LessonPlanNode,
+  TemplateBlockSkeleton,
+} from "../types";
+
+/**
+ * 纯函数模块：课案文档迁移、规范化、初始内容构建。
+ * 从 data-access.ts 抽取，便于单元测试。
+ */
+
+// ---- 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 };
+}
+
+// ---- 类型守卫：判断是否为 v2 文档 ----
+function isV2Document(content: unknown): content is LessonPlanDocument {
+  if (!content || typeof content !== "object") return false;
+  const c = content as { version?: unknown; nodes?: unknown; edges?: unknown };
+  return (
+    c.version === 2 &&
+    Array.isArray(c.nodes) &&
+    Array.isArray(c.edges)
+  );
+}
+
+// ---- 类型守卫：判断是否为 v1 文档 ----
+function isV1Document(content: unknown): content is LessonPlanDocumentV1 {
+  if (!content || typeof content !== "object") return false;
+  const c = content as { version?: unknown; blocks?: unknown };
+  return c.version === 1 && Array.isArray(c.blocks);
+}
+
+// ---- 规范化：确保 content 是 v2 格式（兼容旧数据）----
+export function normalizeDocument(
+  content: unknown,
+): LessonPlanDocument {
+  if (isV2Document(content)) return content;
+  if (isV1Document(content)) return migrateV1ToV2(content);
+  // 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 };
+}

src/modules/lesson-preparation/lib/node-summary.ts

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+import type { LessonPlanNode } from "../types";
+
+/**
+ * 节点摘要翻译函数接口。
+ * 调用方传入 next-intl 的 t 函数，避免纯函数直接耦合 i18n 实现。
+ * values 类型对齐 next-intl 的 TranslationValues（string | number | Date）。
+ */
+export interface NodeSummaryT {
+  (key: "editor.questionCount" | "editor.charCount" | "editor.nodeSummaryEmpty", values?: Record<string, string | number | Date>): string;
+}
+
+/**
+ * 纯函数：获取节点摘要文本（用于节点卡片显示）。
+ * 从 lesson-node.tsx 抽取，便于单元测试。
+ * 翻译文本由调用方通过 t 函数注入，保证纯函数可测性。
+ */
+export function getNodeSummary(node: LessonPlanNode, t: NodeSummaryT): string {
+  const data = node.data as {
+    html?: string;
+    sourceText?: string;
+    items?: unknown[];
+    knowledgePointIds?: string[];
+  };
+  if (data.items !== undefined) {
+    return t("editor.questionCount", { count: data.items.length });
+  }
+  if (data.sourceText !== undefined && data.sourceText) {
+    return t("editor.charCount", { count: data.sourceText.length });
+  }
+  if (data.html) {
+    // 去标签后取前 40 字
+    const text = data.html.replace(/<[^>]+>/g, "").trim();
+    return text.slice(0, 40) || t("editor.nodeSummaryEmpty");
+  }
+  return t("editor.nodeSummaryEmpty");
+}
+
+/**
+ * 节点类型 → 图标颜色（Material Design 色板）。
+ * 供 lesson-node 和 minimap 复用。
+ */
+export const NODE_COLORS: Record<string, string> = {
+  objective: "#4caf50",
+  key_point: "#f44336",
+  import: "#2196f3",
+  new_teaching: "#9c27b0",
+  consolidation: "#ff9800",
+  summary: "#607d8b",
+  homework: "#795548",
+  blackboard: "#009688",
+  text_study: "#3f51b5",
+  exercise: "#e91e63",
+  rich_text: "#9e9e9e",
+  reflection: "#cddc39",
+};
+
+export function getNodeColor(type: string): string {
+  return NODE_COLORS[type] ?? "#9e9e9e";
+}

src/modules/lesson-preparation/lib/rf-mappers.ts

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+import type { Node, Edge } from "@xyflow/react";
+import type { LessonPlanNode, LessonPlanEdge } from "../types";
+
+/**
+ * 纯函数：将课案 nodes/edges 映射为 React Flow 格式。
+ * 从 node-editor.tsx 抽取，便于单元测试。
+ */
+
+export function toRfNodes(
+  nodes: LessonPlanNode[],
+  selectedNodeId: string | null,
+): Node[] {
+  return nodes.map((n) => ({
+    id: n.id,
+    type: "lesson",
+    position: n.position,
+    data: { node: n } as Record<string, unknown>,
+    selected: n.id === selectedNodeId,
+  }));
+}
+
+export function toRfEdges(edges: LessonPlanEdge[]): Edge[] {
+  return edges.map((e) => ({
+    ...e,
+    animated: true,
+    style: { stroke: "#1976d2", strokeWidth: 2 },
+  }));
+}
+
+/**
+ * 将 React Flow edges 转回课案 edges 格式。
+ */
+export function fromRfEdges(
+  rfEdges: Edge[],
+): LessonPlanEdge[] {
+  return rfEdges.map((e) => ({
+    id: e.id,
+    source: e.source,
+    target: e.target,
+    sourceHandle: e.sourceHandle ?? null,
+    targetHandle: e.targetHandle ?? null,
+  }));
+}