Adds an optional lastfmName prop to ArtistModal. When set (only on
/lastfm) it fetches /api/lastfm/artist-plays independently of the
existing preview fetch and renders a most-played-songs list plus a
most-played-albums list above the release grid. Album Want resolves
via /api/mb/release-group then POSTs /api/discover/want, mirroring
the existing want(r) flow. Own-state chips name-match Last.fm albums
against the already-loaded release grid. Other ArtistModal callers
(discover-client.tsx) pass no lastfmName, so their behavior is
unchanged.
Jonathan