Some kind of S3 backend

It's been brought up that it would be nice to have the ability to store or back up tclip data into S3 for long-term recoverability reasons. The goal would be to make sure that pastes survive even if the server gets destroyed.

Personally I've opted for https://github.com/benbjohnson/litestream to sync things - not sure how easy it would be to integrate into tclip itself, or if it's easier to provide instructions to set it up.