ux: Implement a scroll-to-top floating action button

[AlAfiz]

Description

As the pools page gets longer, users will have to scroll heavily to get back to the navigation bar.
We need a small "Scroll to Top" button that appears in the bottom right corner of the screen only after the user scrolls down.
This is a highly appreciated quality-of-life feature for data-heavy applications.
It keeps the user experience smooth and frictionless.

Requirements

• Create a ScrollToTop.tsx component.
• Use a React useEffect to listen to the window.scrollY position.
• Only render the button if the scroll position is greater than 300 pixels.
• When clicked, use window.scrollTo({ top: 0, behavior: 'smooth' }) to smoothly animate back to the top.