Refactor JWT utilities and download token logic

Merged JWT utility functions into utils/JWT/__init__.py and removed utils/JWT/JWT.py. Refactored download token creation and verification to use new functions, replacing DownloadTokenManager with create_download_token and verify_download_token. Updated imports across the codebase to reflect the new JWT utility structure. Improved download file logic to use physical file storage path and added a dedicated response model for download tokens.

routers/api/v1/user/__init__.py

@@ -13,7 +13,7 @@ import models
 import service
 from middleware.auth import auth_required
 from middleware.dependencies import SessionDep
-from utils.JWT.JWT import SECRET_KEY
+from utils.JWT import SECRET_KEY
 from utils import Password, http_exceptions
 
 user_router = APIRouter(