Fix backend imports and package initialization

backend/inference.py

@@ -8,7 +8,7 @@ import sys
 sys.path.append(os.path.abspath(os.path.join(os.path.dirname(__file__), '..')))
 from model.unet import build_unet
 from model.loss_metrics import get_metrics, bce_dice_loss
-from utils.model_fetcher import download_if_missing
+from backend.utils.model_fetcher import download_if_missing
 
 # Force download if missing before initialization
 download_if_missing()