refactor: enhance TimerPage layout and functionality; update theme and tokens for improved design consistency

- Refactored TimerPage component to improve layout and user experience.
- Updated theme configuration to utilize design tokens for better maintainability.
- Introduced new tokens for colors and typography to align with design principles.
- Simplified state management and improved timer functionality.
- Enhanced accessibility and responsiveness of UI elements.

desktop/packaging/kadence.desktop

@@ -7,7 +7,7 @@ Exec=kadence-desktop
 TryExec=kadence-desktop
 Icon=kadence
 Terminal=false
-Categories=Utility;Office;ProjectManagement;
+Categories=Office;ProjectManagement;
 Keywords=pomodoro;timer;focus;tasks;productivity;
 StartupNotify=true
 StartupWMClass=kadence