Replace Selda with something else

[dhess]

It's clear that Selda is unmaintained now. There's at least one community fork, but I'd prefer something where upstream has control over the Hackage story.

Given the future of this project is focused on running most things in-browser, including at least some level of persistence, SQLite support is still attractive, because there's been some success running SQLite in the browser via Wasm. In any case, I think our SQL needs may be quite a bit simpler than we originally anticipated. Therefore, something like https://hackage.haskell.org/package/sqlite-simple might be a good enough replacement for Selda.

Relevant links:

• https://thenitinprakash.com/2021-10-20/Using-Sqlite-with-Haskell