Chore: Consolidate the db-service repo into this one

[lijim]

At $7/ month per server, hosting a separate server for https://github.com/lijim/monks-and-mages-db-service and https://github.com/lijim/monks-and-mages-reverse-proxy is becoming a tad expensive.

This PR consolidates the work in the DB service into the main express app so that the main express app serves all static content, hosts the websocket server, and incorporates DB-accessing API calls (such as fetching all decks for a user) into one singular express app

Pros:

• easier to manage typings if we ever want to share them between services
• less $ spent to host the site

Cons:

• If the DB service aspect has a failure, all the websockets will disconnect because of the Node.JS crash