Clean up backend code

[skybird23333]

Backend code

• The api router is unused and existing API endpoints is not defined in the api router. It should be placed in the routes folder which would be categorised according to API or rendering endpoints.
• The discord module should be treated as a plugin, not something hard coded
• Various features in the admin panel should be registered through a function, so that e.g side panel or actions could be handled dynamically.
• Some test endpoints /test /debug-sentry should be part of admin

Files

• EJS Templates should be categorised according to their feature, e.g post/ or util/.
• Moving unrelated files to a CDN #1