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/config/database.ts

@@ -1,24 +1,16 @@
-import { drizzle } from 'drizzle-orm/mysql2';
-import mysql from 'mysql2/promise';
-import { env } from './env.js';
+import { drizzle } from "drizzle-orm/mysql2";
+import mysql from "mysql2/promise";
+import { env } from "./env.js";
 
-let pool: mysql.Pool | null = null;
+const pool = mysql.createPool({
+  uri: env.DATABASE_URL,
+  waitForConnections: true,
+  connectionLimit: 10,
+  queueLimit: 0,
+});
 
-export function getDb() {
-  if (!pool) {
-    pool = mysql.createPool({
-      uri: env.DATABASE_URL,
-      waitForConnections: true,
-      connectionLimit: 10,
-      queueLimit: 0,
-    });
-  }
-  return drizzle(pool);
-}
+export const db = drizzle(pool);
 
 export async function closeDb(): Promise<void> {
-  if (pool) {
-    await pool.end();
-    pool = null;
-  }
+  await pool.end();
 }

services/content/src/config/env.ts

@@ -1,17 +1,22 @@
-import { z } from 'zod';
+import { z } from "zod";
 
 const envSchema = z.object({
-  PORT: z.string().default('3005'),
+  PORT: z.string().default("3005"),
   DATABASE_URL: z.string().url(),
   REDIS_URL: z.string().url().optional(),
-  NEO4J_URL: z.string().url(),
-  NEO4J_PASSWORD: z.string(),
-  ES_URL: z.string().url(),
-  JWT_SECRET: z.string(),
-  JWT_ISSUER: z.string().default('next-edu-cloud'),
+  NEO4J_URL: z.string().url().optional(),
+  NEO4J_PASSWORD: z.string().optional(),
+  ES_URL: z.string().url().optional(),
+  JWT_SECRET: z.string().optional(),
+  JWT_ISSUER: z.string().default("next-edu-cloud"),
   OTEL_EXPORTER_OTLP_ENDPOINT: z.string().url().optional(),
-  LOG_LEVEL: z.enum(['fatal', 'error', 'warn', 'info', 'debug', 'trace']).default('info'),
-  NODE_ENV: z.enum(['development', 'production', 'test']).default('development'),
+  LOG_LEVEL: z
+    .enum(["fatal", "error", "warn", "info", "debug", "trace"])
+    .default("info"),
+  NODE_ENV: z
+    .enum(["development", "production", "test"])
+    .default("development"),
+  DEV_MODE: z.string().optional().default("false"),
 });
 
 export type Env = z.infer<typeof envSchema>;
@@ -19,8 +24,11 @@ export type Env = z.infer<typeof envSchema>;
 export function loadEnv(): Env {
   const result = envSchema.safeParse(process.env);
   if (!result.success) {
-    console.error('❌ Invalid environment variables:', result.error.flatten().fieldErrors);
-    throw new Error('Invalid environment configuration');
+    console.error(
+      "❌ Invalid environment variables:",
+      result.error.flatten().fieldErrors,
+    );
+    throw new Error("Invalid environment configuration");
   }
   return result.data;
 }

services/content/src/config/neo4j.ts

@@ -1,11 +1,38 @@
-import neo4j from 'neo4j-driver';
-import { env } from './env.js';
+import neo4j from "neo4j-driver";
+import type { Driver, Session } from "neo4j-driver";
+import { env } from "./env.js";
 
-export const neo4jDriver = neo4j.driver(
-  env.NEO4J_URL,
-  neo4j.auth.basic('neo4j', env.NEO4J_PASSWORD)
-);
+// Neo4j driver 创建为惰性初始化：未配置 NEO4J_URL / NEO4J_PASSWORD 时
+// driver 保持 null，服务仍可正常启动。所有依赖 Neo4j 的查询在
+// driver 为 null 时返回空结果或抛出可控错误，不会阻塞主流程。
+let driver: Driver | null = null;
+
+try {
+  if (env.NEO4J_URL && env.NEO4J_PASSWORD) {
+    driver = neo4j.driver(
+      env.NEO4J_URL,
+      neo4j.auth.basic("neo4j", env.NEO4J_PASSWORD),
+      // 连接超时 3s：Neo4j 不可用时快速失败，避免拖慢 HTTP 响应
+      { connectionTimeout: 3000, maxConnectionLifetime: 60_000 },
+    );
+  }
+} catch (err) {
+  console.warn(
+    "Neo4j driver init failed, running without Neo4j:",
+    err instanceof Error ? err.message : String(err),
+  );
+  driver = null;
+}
+
+export function getNeo4jSession(): Session | null {
+  if (!driver) {
+    return null;
+  }
+  return driver.session();
+}
 
 export async function closeNeo4j(): Promise<void> {
-  await neo4jDriver.close();
+  if (driver) {
+    await driver.close();
+  }
 }