Implement Authentication on Frontend (React)

Task: Set up every react page to use isAdmin information for conditional rendering
- write a getProfile endpoint (or similar) that checks if the user is logged in, and if so, returns their user information (everything from their users table row). Pass this information throughout the application so components know how they should conditionally render
- fix all hard coded user information on EVERY page to use the profile information that we request from the backend above
- set up redirects so that users who have not logged in are redirected to the login page. [Checkout this link](https://reactrouter.com/native/example/auth-workflow)