Refactor UI components for improved styling and consistency

Commit notes

- Updated BpmControl to use ThemeIcon for better visual integration. - Enhanced Header component by replacing button text with Title for improved semantics. - Adjusted KeyboardShortcuts ActionIcon color for better visibility. - Modified TransportControls to include ThemeIcon for timer display. - Updated ColorSchemeToggle to use new icon components for a modern look. - Refactored StepGrid to improve margin consistency. - Cleaned up imports in various components for better maintainability.