Add Prisma + DB

[declanramsay]

If we can, I'd like to move away from the express backend and use API routes in the one repository instead.
Combined with TS we'll be able to get type safety for all data from our own tables, which would be very nice.

Blockers/Things to work through migration:

• Authentication
• OIDC Provider for QS

Rough sketch would be:

• Add Prisma and generate schema
• Add all non-auth endpoints
• Move authentication/authorisation over