feat: 닉네임 중복체크 기능 추가

Gameton-06/Assets/Gameton/Resources/UI/Prefabs/UI.CharaterCreateUI.prefab

@@ -407,6 +407,7 @@ MonoBehaviour:
   confirmButton: {fileID: 3290386423334957786}
   createButton: {fileID: 1887714318721360375}
   playerDatas: []
+  nicknameCondition: {fileID: 6220890634190874460}
   characterCreateUI_Modal: {fileID: 7298901665149865196}
   blackCat_Spotlight: {fileID: 6897867871924581457}
   whiteCat_Spotlight: {fileID: 6223168446447065192}
@@ -2140,7 +2141,7 @@ GameObject:
   m_Icon: {fileID: 0}
   m_NavMeshLayer: 0
   m_StaticEditorFlags: 0
-  m_IsActive: 0
+  m_IsActive: 1
 --- !u!224 &898800120090628923
 RectTransform:
   m_ObjectHideFlags: 0

Gameton-06/Assets/Gameton/Scripts/Backend/BackendAuthManager.cs

@@ -94,23 +94,18 @@ namespace TON
         /// </summary>
         public void ChangeNickname(string newNickname, Action<bool, string> callback)
         {
-            if (string.IsNullOrEmpty(newNickname) || newNickname.Length < 2)
-            {
-                callback?.Invoke(false, "닉네임은 2자 이상이어야 합니다.");
-                return;
-            }
 
             Backend.BMember.UpdateNickname(newNickname, bro =>
             {
                 if (bro.IsSuccess())
                 {
                     Debug.Log("닉네임 변경 성공: " + newNickname);
-                    callback?.Invoke(true, "닉네임이 변경되었습니다.");
+                    callback?.Invoke(true, bro.GetCode());
                 }
                 else
                 {
                     Debug.LogError("닉네임 변경 실패: " + bro.GetMessage());
-                    callback?.Invoke(false, "닉네임 변경 실패: " + bro.GetMessage());
+                    callback?.Invoke(false, bro.GetCode());
                 }
             });
         }

Gameton-06/Assets/Gameton/Scripts/UI/CharaterCreateUI.cs

@@ -13,7 +13,7 @@ namespace TON
         [SerializeField] private Button confirmButton; // cancel 버튼 참조
         [SerializeField] private Button createButton; // Create 버튼 참조
         [SerializeField] private List<PlayerData> playerDatas;
-        // [SerializeField] private List<HeartData> heartDatas;
+        [SerializeField] private TextMeshProUGUI nicknameCondition;
 
 
         public GameObject characterCreateUI_Modal;
@@ -25,7 +25,6 @@ namespace TON
         private void Start()
         {
             playerDatas = PlayerDataManager.Singleton.playersData;
-            // heartDatas = HeartDataManager.Singleton.heartDatas;
 
             // 처음에는 버튼을 비활성화
             createButton.interactable = false;
@@ -70,8 +69,9 @@ namespace TON
             string nickname = characterName.text.Trim();
 
             // 입력 값 검증
-            if (string.IsNullOrEmpty(nickname))
+            if (string.IsNullOrEmpty(nickname) || nickname.Length > 12)
             {
+                // 닉네임은 비어있을 수 없고, 12자 이내로만 생성 가능
                 return;
             }
 
@@ -105,11 +105,24 @@ namespace TON
                     }
                     else
                     {
-                        Debug.LogError("캐릭터 닉네임 저장 실패");
+                        // 닉네임 중복체크
+                        if (message.Equals("409"))
+                        {
+                            DuplicateNickname();
+                        }
+                        else
+                        {
+                            Debug.LogError("서버 오류 :: 캐릭터 닉네임 저장 실패");
+                        }
                     }
                 });
             });
+        }
 
+        private void DuplicateNickname()
+        {
+            nicknameCondition.text = "이미 사용중인 이름입니다.";
+            nicknameCondition.color = Color.red;
         }
 
         public void OnClickCancelButton()