Add Lucia Auth to fastify api

[lululeon]

This ticket is to configure Lucia Auth in the fastify backend and implement a minimal database for this purpose.

References:

• https://v2.lucia-auth.com/getting-started/fastify/
• https://v2.lucia-auth.com/guidebook/sign-in-with-username-and-password/
• Can use https://tembo.io/ for a dev postgres instance for now, just for account and user info (not for application info yet; schema tbc).

Acceptance criteria

• implement / add lucia auth middleware
• expose a stub endpoint: auth/signup
• expose a stub endpoint: auth/signin