Move the backend to nextjs

This mean this will be a single service and much more easy to development/deploye and we'll get the benefit of nextjs as well: better router and more

The issue proposes moving the backend to Next.js so the project becomes a single service with easier development and deployment. Start by mapping the existing backend and deployment structure, then define the migration scope and verify that the resulting service preserves current behavior and provides the stated routing and deployment benefits.

Written by the indexing model from the issue text.