auto detect cuda cpu.

app.py

@@ -13,9 +13,14 @@ exec python tools/webui.py ${DEVICE}
 
 import os
 
-CUDA_ENABLED = os.environ.get("CUDA_ENABLED", "true")
-DEVICE = ""
-if CUDA_ENABLED != "true":
-    DEVICE = "--device cpu"
+import torch
+
+if torch.cuda.is_available():
+  DEVICE = "cuda"
+else:
+  DEVICE = "cpu"
+
+DEVICE = f"--device {DEVICE}"
+
 
 os.system(f"python tools/webui.py {DEVICE}")