Simplify sound system with pack-based approach

- Remove complex per-event sound enable/disable settings
- Replace dual volume controls with single "Sound Pack Volume"
- Add "None" sound pack option to disable all sounds
- Fix boolean settings parsing in settings dialog
- Update documentation to reflect simplified sound system

Sound system is now intuitive: select a sound pack (or "None")
and set one volume level. Much cleaner than the previous
per-event checkboxes and confusing dual volume controls.

🤖 Generated with [Claude Code](https://claude.ai/code)

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

README.md

@@ -34,7 +34,8 @@ Bifrost includes a sophisticated sound system with:
 - **One-click Installation**: Download, validate, and install soundpacks securely
 - **Customizable Sound Packs**: Themed audio notifications (Default pack included)
 - **Audio Feedback**: Sound events for all major actions and notifications
-- **Per-event Volume Control**: Fine-tune individual sound effects
+- **Simple Volume Control**: Single volume setting for all sound pack audio
+- **Easy Disable**: Select "None" sound pack to disable all sounds
 - **Cross-platform Audio Support**: Works on Linux, Windows, and macOS
 
 ## Compose Features