Enhance backend API and refactor frontend components for improved user experience

Commit notes

- Added public marketplace routes in the backend API for accessing packs and creators. - Updated frontend components to switch the default color scheme to light mode for better visibility. - Refactored the Header component to use Anchor instead of Link for improved accessibility. - Cleaned up imports and styles in the SampleEditor and DynamicIsland components for better maintainability. - Removed unused styles from app.css to streamline the codebase.