Feature: Add Dark/Light Mode Toggle

[Kritagya123611]

trafficstars

Summary

It would be great to add a Dark/Light mode toggle to the website for better accessibility and user experience.

Benefits

• Improves readability in low-light environments.
• Matches user system preferences.
• Modernizes the website design.

Proposed Solution

• Add a toggle button (🌙/☀️) to the header.
• Use CSS variables for theme colors.
• Persist preference in localStorage.
• Default to system preference (prefers-color-scheme).

Additional context

I’d be happy to implement this and open a PR if the maintainers agree.