Add "Back to Top " Button for Better Navigation

[anuragbraveboy-sudo]

Problem

Users had no easy way to navigate back to the top of long pages while scrolling through menus, dashboards, or order lists.

Solution

Added a floating Back to Top button that:

• Appears after user scrolls 300px down the page
• Fixed position at bottom-right corner of screen
• Smooth scrolls back to top when clicked
• Automatically hides when user is near the top
• Fully responsive on both mobile and desktop

Changes

• Created new BackToTop.jsx component
• Imported and integrated in Landing.jsx

Closes

Fixes rdodiya#58

## Screenshot