Update Cart Feature: Add Quantity Controls and Change 'Add to Cart' to 'Continue to Checkout'

[jimmyurl]

This pull request refactors the cart functionality on the product page. The previous 'Add to Cart' button has been replaced with a quantity adjustment interface. Users can now increase or decrease the quantity of the selected item and proceed to checkout with a new 'Continue to Checkout' button. Changes Made

• Removed the 'Add to Cart' button.
• Added quantity adjustment controls (+ and -) for each product.
• Replaced the old button with a 'Continue to Checkout' button.
• Updated the CSS to reflect changes in the product page layout.

Please review the changes and provide feedback. Thank you!