Amazon is back up, and our host (Heroku) is bringing stuff back online, so we should be up again shortly.
In future, I've learned we need to have better contingency plans lined up. This specific problem has never happened before (and likely will never happen again), but we made the mistake of depending on one (to be fair, highly reliable!) hosting service.
Next time, I'll be prepared with the ability to start Kitsu servers with other hosting providers. I wasn't able to set that up fast enough today