Sweep round 4: 5 more httptest handlers in provider_theaudiodb_test.go
where r is unused. Lint flagged 3 (lines 89/103/118); also fixing
2 more (TestConnection_SuccessOnEmptyAlbum, FailureOn401) that lint
would catch on the next run. The 4 handlers that DO use r.URL.Path
or r.Host are left as-is.