feat(web): Last.fm most-played songs + albums in the artist modal

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.

web/src/app/lastfm/lastfm-client.tsx

@@ -304,7 +304,13 @@ export function LastfmClient() {
       ) : null}
 
       {artistModal ? (
-        <ArtistModal open onClose={() => setArtistModal(null)} mbid={artistModal.mbid} initialName={artistModal.name} />
+        <ArtistModal
+          open
+          onClose={() => setArtistModal(null)}
+          mbid={artistModal.mbid}
+          initialName={artistModal.name}
+          lastfmName={artistModal.name}
+        />
       ) : null}
 
       {albumTarget ? (