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/main.ts

@@ -1,31 +1,46 @@
-import 'reflect-metadata';
-import { NestFactory } from '@nestjs/core';
-import { AppModule } from './app.module.js';
-import { GlobalErrorFilter } from './shared/errors/global-error.filter.js';
-import { initTracer, shutdownTracer } from './shared/observability/tracer.js';
-import { env } from './config/env.js';
-import { logger } from './shared/observability/logger.js';
+import "reflect-metadata";
+import { NestFactory } from "@nestjs/core";
+import { AppModule } from "./app.module.js";
+import { GlobalErrorFilter } from "./shared/errors/global-error.filter.js";
+import { initTracer, shutdownTracer } from "./shared/observability/tracer.js";
+import { env } from "./config/env.js";
+import { closeDb } from "./config/database.js";
+import { closeNeo4j } from "./config/neo4j.js";
+import { logger } from "./shared/observability/logger.js";
 
 async function bootstrap(): Promise<void> {
   initTracer();
 
   const app = await NestFactory.create(AppModule, {
-    logger: ['log', 'error', 'warn'],
+    logger: ["log", "error", "warn"],
   });
 
   app.useGlobalFilters(new GlobalErrorFilter());
   app.enableShutdownHooks();
 
   await app.listen(env.PORT);
-  logger.info({ port: env.PORT }, 'Content service started');
+  logger.info({ port: env.PORT }, "Content service started");
 
-  process.on('SIGTERM', async () => {
-    await app.close();
+  process.on("SIGTERM", async () => {
+    logger.info("SIGTERM received, shutting down gracefully...");
+    await closeNeo4j();
+    await closeDb();
     await shutdownTracer();
+    await app.close();
+    process.exit(0);
+  });
+
+  process.on("SIGINT", async () => {
+    logger.info("SIGINT received, shutting down gracefully...");
+    await closeNeo4j();
+    await closeDb();
+    await shutdownTracer();
+    await app.close();
+    process.exit(0);
   });
 }
 
 bootstrap().catch((err: unknown) => {
-  logger.error({ err }, 'Failed to start content service');
+  logger.error({ err }, "Failed to start content service");
   process.exit(1);
 });