Add @spaces.GPU decorator to inference function for ZeroGPU

ZeroGPU requires at least one @spaces.GPU-decorated function at startup.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/appfunc.py

@@ -2,6 +2,7 @@ import os
 import random
 import traceback
 import gradio as gr
+import spaces
 import os.path as osp
 
 from huggingface_hub import hf_hub_download, list_repo_files
@@ -171,6 +172,7 @@ def set_cas_scales(accurate, cas_args):
     return scale_strength
 
 
+@spaces.GPU(duration=120)
 @torch.no_grad()
 def inference(
         style_enhance, bg_enhance, fg_enhance, fg_disentangle_scale,