Migrate to Postgres DB

[Enniwhere]

Description:
SQLite is a bit too immature for our needs with regards to vector indexes, so we probably want to move to Postgres to get more features.

Acceptance criteria:

• Investigate and estimate the cost of moving to postgres
• Move the database to postgres and host it as a service on the production server

Technical details:
Optional technical details for context.

Design:
Optional details on design for context.