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/shared/lifecycle/lifecycle.service.ts

@@ -1,63 +1,24 @@
-import { Inject, Injectable, Logger, OnApplicationShutdown, OnModuleInit } from '@nestjs/common';
-import { DataSource } from 'typeorm';
-import type { Redis } from 'ioredis';
-import type { Producer } from 'kafkajs';
+import { Injectable, Logger } from "@nestjs/common";
+import { closeDb } from "../../config/database.js";
+import { closeNeo4j } from "../../config/neo4j.js";
 
-const SERVICE_NAME = 'content';
+const SERVICE_NAME = "content";
 
-/**
- * 优雅停机服务。
- *
- * 信号处理由 NestJS 在 `app.listen` 之前调用 `app.enableShutdownHooks()`
- * 触发（SIGTERM / SIGINT），NestJS 会依次调用 OnApplicationShutdown 钩子。
- * K8s 配置 `terminationGracePeriodSeconds=60` 给予足够时间清理。
- *
- * 关闭顺序：Kafka producer → Redis → DataSource。
- * 先停外部消息生产避免新事件，再关缓存，最后关 DB。
- * 注：content 服务额外使用 S3/MinIO 客户端，其连接由 SDK 内部管理，无需显式关闭。
- *
- * 集成说明（不修改 app.module.ts，仅在 README 注释说明）：
- * - 在 `app.module.ts` 的 providers 中加入 `LifecycleService`。
- * - 在 `main.ts` 中 `app.listen` 之前调用 `app.enableShutdownHooks()`。
- *
- * 依赖注入 token 约定（需与各服务 provider 注册一致）：
- * - DataSource：由 `TypeOrmModule.forRoot()` 提供。
- * - 'REDIS_CLIENT'：需在对应模块注册 `{ provide: 'REDIS_CLIENT', useFactory: ... }`。
- * - 'KAFKA_PRODUCER'：需在对应模块注册 `{ provide: 'KAFKA_PRODUCER', useFactory: ... }`。
- */
 @Injectable()
-export class LifecycleService implements OnModuleInit, OnApplicationShutdown {
+export class LifecycleService {
   private readonly logger = new Logger(LifecycleService.name);
 
-  constructor(
-    private readonly dataSource: DataSource,
-    @Inject('REDIS_CLIENT') private readonly redis: Redis,
-    @Inject('KAFKA_PRODUCER') private readonly kafkaProducer: Producer,
-  ) {}
-
-  onModuleInit(): void {
-    this.logger.log(`service ${SERVICE_NAME} module initialized`);
-  }
-
   async onApplicationShutdown(signal?: string): Promise<void> {
     this.logger.log(
-      `service ${SERVICE_NAME} shutting down (signal=${signal ?? 'unknown'})`,
+      `service ${SERVICE_NAME} shutting down (signal=${signal ?? "unknown"})`,
     );
-
-    await this.safeDisconnect('kafka producer', () => this.kafkaProducer.disconnect());
-    await this.safeDisconnect('redis', () => this.redis.quit());
-    await this.safeDisconnect('datasource', () => this.dataSource.destroy());
-
-    this.logger.log(`service ${SERVICE_NAME} shutdown complete`);
-  }
-
-  private async safeDisconnect(name: string, fn: () => Promise<unknown>): Promise<void> {
     try {
-      await fn();
-      this.logger.log(`${name} closed`);
+      await closeNeo4j();
+      await closeDb();
+      this.logger.log(`service ${SERVICE_NAME} shutdown complete`);
     } catch (error) {
       this.logger.error(
-        `${name} close failed: ${error instanceof Error ? error.message : String(error)}`,
+        `shutdown failed: ${error instanceof Error ? error.message : String(error)}`,
       );
     }
   }