Replace In-Memory UUID Dict with SQLite Database

(Discussed at WolfCon 2023):

Currently, the Folio Migration process uses in-memory dictionaries to verify the existence of UUIDs.

Unfortunately, for large data sets, holding this in-memory is causing problems and delays.

We should switch long-term to a flexible database connection option - allowing for distributed task runners to share a database - but first, we can use a local SQLite file to validate.