Replace JSON with stringified JSON in database, make default database local sqlite

[lalalune]

We want to remove the docker dependency so that users can quickstart without it, using a local sqlite instance. However, our current models use JSON. We can dynamically set which we startup with, but only if the models use the same supported features.

• Replace JSON with stringified JSON in models
• Make sure calls are creating JSON from the returned text
• Add default to sqlite in model and .env
• Update README