노래 만들기 수정 — NAS 업로드 완성, Easy 제거 및 ExpertPlus 추가, 다운로드 버그 수정

- NasPublisher: DSM 7.2 multipart body 수동 구성으로 업로드 401 오류 해결
- NasPublisher: 비밀번호 StreamingAssets/nas_config.json 분리, .gitignore 등록
- NasPublisher: staticBaseUrl 포트 8180 → 80 수정
- BeatSageUploader: Easy 난이도 제거, ExpertPlus(.dat) 추가
- NoteData: DifficultyMap에서 easy 제거, expertplus 추가
- SongCreatorManager: toggleEasy → toggleExpertPlus 교체
- SongDetailPanel: btnEasy → btnExpertPlus 교체
- DownloadManager: DownloadHandlerFile 경로 정규화(Path.GetFullPath), mapFile 빈 값 방어 처리
- PersistentXRRig: FindObjectsOfType obsolete 경고 수정

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

Assets/Script/SongDetailPanel.cs

@@ -13,15 +13,16 @@ public class SongDetailPanel : MonoBehaviour
     [SerializeField] private TMP_Text infoText;
 
     [Header("난이도 버튼")]
-    [SerializeField] private Button btnEasy;
     [SerializeField] private Button btnNormal;
     [SerializeField] private Button btnHard;
     [SerializeField] private Button btnExpert;
+    [SerializeField] private Button btnExpertPlus;
 
     [Header("액션 버튼")]
     [SerializeField] private Button downloadButton;
     [SerializeField] private Button deleteButton;
     [SerializeField] private Button playButton;
+    [SerializeField] private Button closeButton;
 
     [Header("진행률")]
     [SerializeField] private GameObject progressGroup;
@@ -41,10 +42,10 @@ public class SongDetailPanel : MonoBehaviour
 
     private readonly (string key, System.Func<SongDetailPanel, Button> btn)[] diffSlots =
     {
-        ("easy",   p => p.btnEasy),
-        ("normal", p => p.btnNormal),
-        ("hard",   p => p.btnHard),
-        ("expert", p => p.btnExpert),
+        ("normal",     p => p.btnNormal),
+        ("hard",       p => p.btnHard),
+        ("expert",     p => p.btnExpert),
+        ("expertplus", p => p.btnExpertPlus),
     };
 
     // ── Public API ───────────────────────────────────────────
@@ -101,6 +102,9 @@ public class SongDetailPanel : MonoBehaviour
 
         playButton.onClick.RemoveAllListeners();
         playButton.onClick.AddListener(OnPlayClicked);
+
+        closeButton?.onClick.RemoveAllListeners();
+        closeButton?.onClick.AddListener(() => gameObject.SetActive(false));
     }
 
     private void SelectDifficulty(string difficulty)