Feat: 세션 상태 정보/응답 DTO 추가

Author: jueunk617

src/main/java/com/back/global/websocket/dto/WebSocketSessionInfo.java

@@ -0,0 +1,4 @@
+package com.back.global.websocket.dto;
+
+public class WebSocketSessionInfo {
+}

src/main/java/com/back/global/websocket/dto/WebSocketStatusResponse.java

@@ -0,0 +1,4 @@
+package com.back.global.websocket.dto;
+
+public class WebSocketStatusResponse {
+}