Login page styling broken on small screen heights

[timroes]

When the screen height is too small (that you'll need to scroll) the login page design gets broken:

The left background should extend fully to the bottom as well as the right panel should fill the whole page space even when scrollable. The right panel also needs to be tested with the authPage.rightSideUrl experimentation setting on, that the iFrame renders correctly in this case.

[octavia-squidington-iii]

cc @airbytehq/frontend