Complete re-write

[BoscoDomingo]

Made massive improvements. Most major changes:

• Update to TypeScript 5.5.4
• Use Fastify instead of Express
• Use Node Test Runner instead of Jest
• Use Biome instead of ESLint + Prettier
• Use tsx instead of ts-node-dev

General improvements to cleanliness, usefulness of the repo, added some tests.

Left to do is to correctly organise into folders to turn it into a monorepo (will still be compatible with single-app developments)

[AlexHHPS]

LGTM