Fix Gradio 6 queue launch API

app.py

@@ -127,4 +127,5 @@ def build_demo():
 demo = build_demo()
 
 if __name__ == "__main__":
-    demo.queue(concurrency_count=1).launch()
+    # Gradio 6 removed concurrency_count kwarg; use default queue
+    demo.queue().launch()