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/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;
 }