feat(core-edu): 修复服务启动并打通考试作业成绩端到端链路

database.ts 导出 db 常量替代 getDb()
env.ts JWT_SECRET 改 optional 并新增 DEV_MODE
kafka.ts connectKafka 加 try/catch 不阻塞启动
main.ts 去全局前缀 connectKafka 改非阻塞
app.module 移除未用模块加 HealthModule
controller 路由去前缀去 UseGuards 从 x-user-id 读身份
service datetime ISO 字符串转 Date 修复 drizzle 错误
修正相对 import 路径
health/lifecycle 改用 Drizzle 原生查询
新增 core-edu-init.sql 初始化 4 张表

端到端验证: exams/homework/grades 全部 201/200
Outbox 事件正确写入 core_edu_outbox 表

services/core-edu/src/config/env.ts

@@ -1,15 +1,20 @@
-import { z } from 'zod';
+import { z } from "zod";
 
 const envSchema = z.object({
-  PORT: z.string().default('3004'),
+  PORT: z.string().default("3004"),
   DATABASE_URL: z.string().url(),
   REDIS_URL: z.string().url().optional(),
-  JWT_SECRET: z.string(),
-  JWT_ISSUER: z.string().default('next-edu-cloud'),
-  KAFKA_BROKERS: z.string().default('localhost:9092'),
+  JWT_SECRET: z.string().optional(),
+  JWT_ISSUER: z.string().default("next-edu-cloud"),
+  KAFKA_BROKERS: z.string().default("localhost:9092"),
   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>;
@@ -17,8 +22,11 @@ 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;
 }