feat: SongCreator 씬 완성 — Beat Sage URL 지원, info.dat 메타데이터 자동 추출

- BeatSageUploader: audio_url 지원(UploadFromUrl), PollAndDownload 공통화, ZIP 500 오류 3회 재시도
- BeatSageConverter: info.dat 파싱(SongMetadata), BPM 자동 감지 → 노트 타이밍 변환에 적용
- SongCreatorManager: title/BPM 필수 입력 제거, 난이도 4개 자동 선택, GenerateFlowFromUrl 버그 수정
- NasPublisher: audioPath null 허용(URL 흐름에서 로컬 파일 없는 경우 스킵)
- .gitignore/.gitattributes 초기 설정

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

Assets/VRBeatsKit/Modules/VRSDK/VR/Input/VR_InputDevice.cs

@@ -0,0 +1,38 @@
+using UnityEngine;
+
+namespace VRSDK
+{
+    /// <summary>
+    /// Supported Inputs
+    /// </summary>
+    public enum VR_InputButton
+    {
+        None,
+        Primary,
+        Secondary,
+        Trigger,
+        Grip,
+        TumbstickPress    
+    }
+
+    public abstract class VR_InputDevice
+    {
+        protected VR_Controller InputController { get; private set; }
+
+        public VR_InputDevice(VR_Controller controller)
+        {
+            this.InputController = controller;
+        }
+
+        public abstract Quaternion GetRotationOffset();
+        public abstract Vector3 GetPositionOffset();
+        public abstract string GetDeviceName();                
+        public abstract float GetAxis1D(VR_InputButton button);
+        public abstract Vector2 GetJoystick();
+        public abstract bool GetButtonDown(VR_InputButton button);
+        public abstract bool GetButtonUp(VR_InputButton button);
+        public abstract bool GetButton(VR_InputButton button);        
+        public abstract bool IsConnected();
+        public abstract System.Enum GetControllerType();
+    }
+}