Added Dark Mode

[NothingADSR123]

Summary

This pull request resolves issue #5 by implementing a series of UI enhancements and adding a new dark mode feature.

Key Changes Implemented:

• UI Enhancements:

  • Refactored layout for better spacing and responsiveness.
  • Improved color contrast and font sizes for accessibility.
  • Polished button styles and form inputs for a modern look.

• New Feature: Dark Mode

  • Added a theme toggle button (Sun/Moon icon) in the header.
  • User's theme preference is persisted in localStorage.
  • All components, including modals and the syntax highlighter, now adapt correctly to the selected theme.

This improves the overall user experience and modernizes the application's design.

Closes #5