refractor for HHD and depth backend

src/orisys/get_depth.py

@@ -1,14 +1,8 @@
 import numpy as np
 import cv2
 
-# Try to import CuPy for GPU acceleration
-try:
-    import cupy as cp
-    CUPY_AVAILABLE = True
-except ImportError:
-    cp = None
-    CUPY_AVAILABLE = False
-
+from .backend_availability import CUPY_AVAILABLE, get_cupy
+cp = get_cupy()
 # 缓存形态学操作的核，避免重复创建
 _morphology_kernels = {}