fix: return install error in status field instead of raising

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

app.py

@@ -305,7 +305,10 @@ def gradio_infer(
     save_scores, flip, size, reverse
 ):
     # <<< ZeroGPU 分配后：按需安装 Pytorch-Correlation-extension >>>
-    ensure_correlation_extension_installed()
+    try:
+        ensure_correlation_extension_installed()
+    except Exception as install_err:
+        return None, f"spatial-correlation-sampler install failed:\n{install_err}"
     # --------------------------------------------------------------
 
     # 1) 基本校验与临时目录