The previous implementation called LookupArtist (rate-limited MB API)
before fetching url-rels, wasting a rate limiter slot. The fetchURL
for rels also bypassed the MB rate limiter, risking 503 rejections.
Rewrite: fetch MB url-rels once (direct HTTP, cached 30 days), parse
both image and wikidata relations from the same response, resolve
Wikimedia thumb URL. No dependency on MusicBrainzClient — just the
Cache for storage and a plain http.Client.
Also cleared 34 stale cached empty results from previous failed
resolution attempts that were blocking image lookup.
yonlu
104e469774