elitan collapses Mike into a single app

The fork's separate API server is gone - frontend and backend now live inside one Next.js project.

Until this change, Mike ran as two pieces: a standalone server that handled data and authentication, talking to a separate web app for the user interface. elitan merged them, moving all the server logic inside the web app itself and routing API calls through a unified prefix.

Alongside the move, elitan swapped in oRPC - a layer that lets the frontend call backend functions with full type safety, so a change on one side immediately surfaces as an error on the other if it breaks the contract. TanStack Query, a library for managing how the UI fetches and caches data, was wired in at the same time. File uploads, downloads, and live event streams were deliberately left on the old paths to avoid breaking anything during the cutover.