Feature/theme toggle

[Truphile]

I've completed the implementation of the theme toggle functionality for your project!

Here is a summary of the actions taken:

1. Created a new branch called feature/theme-toggle.
2. Installed next-themes to handle dark, light, and system theme modes.
3. Created ThemeProvider (components/theme-provider.tsx) and wrapped it around the main application layout in
   app/layout.tsx. It uses the class attribute, tying it smoothly into Tailwind CSS's dark: classes to avoid
   unstyled content flashes.
4. Created a new ThemeToggle component (components/theme-toggle.tsx) that leverages Lucide icons and seamlessly
   transitions between dark and light modes.
5. Integrated ThemeToggle into the Navigation bar (components/nav.tsx) alongside the ConnectButton.
6. Committed all the changes to the new branch as requested.

The application should now fully support persistent switching between themes with no flashes, persisting user
choice across sessions! Let me know if there's anything else you'd like to adjust.

closes #231