Compound Interest Calculator - Simplified Site Colors, Tooltips for All Inputs, Instructions

The Compound Interest Calculator interface has been updated with a cleaner visual style based on the site's core colors. Excessive accent gradients were reduced to improve focus and overall readability. Additionally, tooltips have been added for all input fields to provide users with quick explanations of each parameter, and a comprehensive instructions section has been included to guide users through the process of calculating compound interest effectively.