Show user/guest icon in header

[js0mmer]

Show the user icon in the collapsed sidebar so that the user can easily see whether or not they are logged in. Show a login button instead if the user is not logged in.

Another idea would be to put the user profile/log in button in the top right which is a more conventional place. Have a dropdown for it with the log out button and other profile tabs/settings (dark mode toggle & reviews to be added in future).

Here are some ideas I've mocked up.

For the mobile one, I borrowed some ideas from #239. Designs are not final and I'm still not sure what the mobile header would look like on other pages (without the course/professor toggle). I also moved the tabs to the bottom on the mobile design mock-up since I don't think a full screen expanding menu is needed for two tabs and this will make navigation quicker. I drew inspiration from YouTube and Twitter's mobile sites for this. Also when using the site as a guest, would probably still want a dropdown/toggle for changing the theme (once dark mode is complete).