feat(msg): 修复通知服务并添加ES降级与Push Gateway推送

database.ts 导出db常量替代getDb()函数

env.ts JWT_SECRET/ES_URL改optional加DEV_MODE/PUSH_GATEWAY_URL

elasticsearch.ts ES降级: ES_URL未设置时esClient=null

notifications.service.ts 加createBatch+分页查询+Push Gateway推送调用

新建msg-init.sql创建2张表

services/msg/package.json

@@ -32,6 +32,7 @@
   "devDependencies": {
     "@nestjs/cli": "^10.4.0",
     "@types/node": "^22.0.0",
+    "@types/uuid": "^10.0.0",
     "typescript": "^5.6.0",
     "vitest": "^2.1.0"
   }