Add missing app.launch() command

backend/app.py

@@ -118,3 +118,4 @@ with gr.Blocks(theme=gr.themes.Soft()) as app:
         app.load(fn=show_history, outputs=history_df)
         refresh_history_btn.click(fn=show_history, outputs=history_df)
         submit_feedback_btn.click(fn=save_feedback_and_refresh, inputs=[record_id_input, feedback_label], outputs=[history_df, feedback_status])
+app.launch()