feat(content): 修复服务并添加chapters/knowledge-points/questions模块

- database.ts 导出db常量替代getDb()函数

- env.ts JWT_SECRET/ES_URL/NEO4J_URL改optional加DEV_MODE

- neo4j.ts driver惰性创建+try/catch+connectionTimeout:3000

- health/lifecycle改用Drizzle原生查询

- textbooks.schema修复integer到int+导出NewTextbook类型

- 新建chapters/knowledge-points/questions三模块CRUD

- knowledge-points含Neo4j前置依赖图非阻塞查询

- content-init.sql创建4张表

端到端验证: textbooks/chapters/knowledge-points/questions全CRUD通过

services/content/src/app.module.ts

@@ -1,7 +1,17 @@
-import { Module } from '@nestjs/common';
-import { TextbooksModule } from './textbooks/textbooks.module.js';
+import { Module } from "@nestjs/common";
+import { TextbooksModule } from "./textbooks/textbooks.module.js";
+import { ChaptersModule } from "./chapters/chapters.module.js";
+import { KnowledgePointsModule } from "./knowledge-points/knowledge-points.module.js";
+import { QuestionsModule } from "./questions/questions.module.js";
+import { HealthModule } from "./shared/health/health.module.js";
 
 @Module({
-  imports: [TextbooksModule],
+  imports: [
+    TextbooksModule,
+    ChaptersModule,
+    KnowledgePointsModule,
+    QuestionsModule,
+    HealthModule,
+  ],
 })
 export class AppModule {}