Add Dark Mode Option to Project Interface

[StevenZhou795]

To improve user experience, add a dark mode option in the settings menu that allows users to toggle between light and dark themes.
Users can toggle between light and dark themes without issues.
Dark mode should be visually consistent and maintain readability.

[StevenZhou795]

To make it easier to switch between light and dark themes, define color variables for each theme. Implement with CSS or a similar styling system, where we define colors for both light and dark themes.