Added history and memory functionality with hover effects

Pull Request Description

In this pull request, I've introduced two significant enhancements to the project:

History and Memory Functionality: I've added the capability to store previous calculations in a history log and save specific results to memory for later use. This functionality allows users to keep track of their calculations and easily recall important results. Resolved #1
Hover Effects: I've also implemented hover effects to improve the user experience. Buttons now respond to hover actions, making the interface more interactive and user-friendly. Partially resolved #5

I've attached a video demonstration for your review