Fix ProjectService param and Gradio 6 Audio component

- Fix ProjectService: db -> database
- Remove show_download_button from gr.Audio (Gradio 6.x)

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

main.py

@@ -71,7 +71,7 @@ async def initialize_services():
     )
 
     project_service = ProjectService(
-        db=db,
+        database=db,
         output_dir=settings.output_dir,
     )