refactor: rename frontend/ to web-player/ and format with prettier

Updates the compose build context, the Dockerfile header, the package
name and the docs. The compose service and container keep the name
frontend/musify-frontend, since nginx routes to http://frontend:3000.

The source files also carry the first prettier pass, so the rename and
the reformat land together for them.

web-player/src/lib/config.ts

@@ -0,0 +1,3 @@
+export const EXPLORE_PAGE_SIZE = 27;
+export const HOME_LATEST_PAGE_SIZE = 12;
+export const YOUTUBE_FILLER_LIMIT = 27;