Fix: delay spaces import until after GPU functions are defined

gradio_app.py

@@ -44,6 +44,7 @@ from fastapi import FastAPI
 from fastapi.staticfiles import StaticFiles
 import uuid
 import numpy as np
+import spaces  # needed for @spaces.GPU decorator
 
 from hy3dshape.utils import logger
 from hy3dpaint.convert_utils import create_glb_with_pbr_materials