getOidcConfig() memoized the discovery promise even when it rejected,
so a single failed OIDC discovery (e.g. Zitadel not ready yet when the
dev server starts) permanently broke /auth/login until the process was
restarted. Clear the cached promise on rejection so it retries.
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.