feat(chat): 외부 캐릭터 챗 세션 API URL 수정

- /api/session/... -> /api/sessions/...

src/main/kotlin/kr/co/vividnext/sodalive/chat/room/service/ChatRoomService.kt

@@ -150,7 +150,7 @@ class ChatRoomService(
             val httpEntity = HttpEntity(requestBody, headers)
 
             val response = restTemplate.exchange(
-                "$apiUrl/api/session",
+                "$apiUrl/api/sessions",
                 HttpMethod.POST,
                 httpEntity,
                 String::class.java
@@ -238,7 +238,7 @@ class ChatRoomService(
             val httpEntity = HttpEntity(null, headers)
 
             val response = restTemplate.exchange(
-                "$apiUrl/api/session/$sessionId",
+                "$apiUrl/api/sessions/$sessionId",
                 HttpMethod.GET,
                 httpEntity,
                 String::class.java
@@ -307,7 +307,7 @@ class ChatRoomService(
                 val httpEntity = HttpEntity(null, headers)
 
                 val response = restTemplate.exchange(
-                    "$apiUrl/api/session/$sessionId/end",
+                    "$apiUrl/api/sessions/$sessionId/end",
                     HttpMethod.PUT,
                     httpEntity,
                     String::class.java