Add Authentication and Improve Unprofessional UI Design

Currently, the project lacks an authentication system, allowing unrestricted access to all features. I will be adding secure user authentication (sign up, login, logout) and implementing a backend using the MERN stack (MongoDB, Express, React, Node.js) to manage user data effectively.

Additionally, the existing UI is unprofessional and needs improvement. I plan to redesign it with a cleaner layout, modern styling, and better responsiveness to provide a polished and user-friendly experience.

Start by inspecting the existing project structure, UI entry points, and data flow before planning the MERN backend and authentication flow. Done means sign-up, login, and logout restrict access appropriately, user data is managed securely, and the interface has a cleaner, responsive redesign.

Written by the indexing model from the issue text.