Admin UI should do auth check before rendering content

When first visiting the app, the main page is rendered and visible for a second or two before the login page appears. This isn't that big of a deal, just weird. The bigger issue is if I am on a page listing a bunch of variant info and then logout, when I hit the back button I see all of that variant info and have plenty of time (1-2 seconds) to take a screenshot before the login screen appears.