feat: add SFX volume control and improve audio feedback

- Implemented separate sound effects volume control in settings.
- Updated backend to handle new `sfx_volume` parameter.
- Enhanced UI to include sound effects volume slider in admin panel.
- Integrated sound effects for various user interactions (clicks, navigation, alerts).
- Added a new global sound engine to manage audio synthesis without external files.
- Updated documentation for Docker deployment and Windows packaging.
- Refactored audio context management to ensure sound effects are available post user interaction.

backend/app/admin.py

@@ -72,6 +72,7 @@ async def admin_page(request: Request):
             "play_mode": s.get("play_mode", "sequential"),
             "image_duration": s.get("image_duration", 5),
             "volume": s.get("volume", 80),
+            "sfx_volume": s.get("sfx_volume", 60),
             "fullscreen": s.get("fullscreen", True),
             "autostart": s.get("autostart", False),
             "from_screen": request.query_params.get("from") == "screen",