fix(music-lab): VIDEO_DATA_DIR 기본값 통일 + lazy import 정리

- VIDEO_DATA_DIR 기본값을 /app/data/videos로 수정 (기존 /app/data에 videos 서브디렉토리를 중복 붙이던 버그 수정)
- delete_project, export_project의 경로에서 중복된 "videos" 서브디렉토리 제거
- create_project 내부의 get_track_by_id lazy import를 파일 상단 import 블록으로 이동

music-lab/app/main.py

@@ -10,7 +10,7 @@ from pydantic import BaseModel
 from .db import (
     init_db,
     create_task, get_task,
-    get_all_tracks, add_track, delete_track, get_track_file_path, get_track_by_task_id,
+    get_all_tracks, add_track, delete_track, get_track_file_path, get_track_by_task_id, get_track_by_id,
     update_track_duration, update_track_file_info, update_track_hash,
     get_all_lyrics, add_lyrics, update_lyrics, delete_lyrics,
     create_video_project, get_video_project, get_all_video_projects,
@@ -39,7 +39,7 @@ app.add_middleware(
 )
 
 MUSIC_DATA_DIR = "/app/data"
-VIDEO_DATA_DIR = os.getenv("VIDEO_DATA_DIR", "/app/data")
+VIDEO_DATA_DIR = os.getenv("VIDEO_DATA_DIR", "/app/data/videos")
 
 
 def _get_mp3_duration(file_path: str) -> Optional[int]:
@@ -712,7 +712,6 @@ class RevenueUpdate(BaseModel):
 
 @app.post("/api/music/video-project", status_code=201)
 def create_project(req: VideoProjectCreate, background_tasks: BackgroundTasks):
-    from .db import get_track_by_id
     if not get_track_by_id(req.track_id):
         raise HTTPException(status_code=404, detail="Track not found")
     if req.format not in ("visualizer", "slideshow"):
@@ -753,7 +752,7 @@ def export_project(project_id: int):
         raise HTTPException(status_code=404, detail="Project not found")
     if proj["status"] != "done":
         raise HTTPException(status_code=400, detail=f"렌더링 미완료 (status: {proj['status']})")
-    meta_path = os.path.join(VIDEO_DATA_DIR, "videos", str(project_id), "metadata.json")
+    meta_path = os.path.join(VIDEO_DATA_DIR, str(project_id), "metadata.json")
     metadata = {}
     if os.path.exists(meta_path):
         with open(meta_path, encoding="utf-8") as f:
@@ -774,7 +773,7 @@ def export_project(project_id: int):
 def delete_project(project_id: int):
     if not get_video_project(project_id):
         raise HTTPException(status_code=404, detail="Project not found")
-    out_dir = os.path.join(VIDEO_DATA_DIR, "videos", str(project_id))
+    out_dir = os.path.join(VIDEO_DATA_DIR, str(project_id))
     if os.path.isdir(out_dir):
         shutil.rmtree(out_dir, ignore_errors=True)
     delete_video_project(project_id)