fix(iot-gateway): 修正RPC环境变量名不匹配导致连接失败

docker-compose中VIEWSH_IOT_GATEWAY_RPC_URL与yaml期望的VIEWSH_GATEWAY_RPC_URL不一致，
导致iot-gateway回退到默认值127.0.0.1:48091，容器间无法通信。

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

docker-compose.core.yml

@@ -212,7 +212,7 @@ services:
       
       ROCKETMQ_NAME_SERVER: rmq-4wd73bxpv.rocketmq.sh.qcloud.tencenttdmq.com:8080
       # 添加这一行
-      VIEWSH_IOT_GATEWAY_RPC_URL: "http://aiot-iot-server:48091"
+      VIEWSH_GATEWAY_RPC_URL: "http://aiot-iot-server:48091"
     volumes:
       - app-logs:/app/logs
     deploy: