FE-08: Dark / Light Mode Toggle

[jpdevhub]

The Idea

Currently, FreshScan AI is dark-mode only. Let's add a light theme and a system-aware toggle to make the app more accessible!

What needs to be done

• Implement a theme toggle in the Navbar.
• Store the user's preference in localStorage.
• Ensure the app respects the OS-level prefers-color-scheme media query.

A perfect, high-visibility first issue for UI lovers!

[atmihaa-06]

I'd love to take on this issue! I've been working on improving the UI and error handling, and I'm familiar with the codebase. I plan to implement the toggle in the Navbar and use localStorage to persist the user's preference. Please assign it to me.

[jpdevhub]

Awesome, I have assigned FE-08 to you!
To get the PR merge smoothly you have to stick to these contrainsts:

1. Use tailwind's native system strictly v4 dark modifier class.
2. The app should check the system preference first.
3. Eliminate the white flash. You must implement small blocking inline script that reads the local storage and applies the dark class to the html tag before the react bundle executes.
4. Dynamic PWA status bar: the toggle must programatically update the theme color tag in DOM.
   looking forward to your pr!