feat: the Wanted view lists artists A–Z with their albums inside, each album's tracks a click away (M502 #5572)

The list runs like the library: artists by the library's sort name, each
artist's albums oldest first, grouped under the artist (linked into the
library when it holds them). A filter narrows it to an artist or album by
name, on the server, so it finds what has not been scrolled to. Tracks
opens an album's track list: the library's own for an album it holds, a
lost file marked, otherwise MusicBrainz's standard edition, named.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/api/api.go

@@ -257,6 +257,7 @@ func Mount(r chi.Router, pool *pgxpool.Pool, logger *slog.Logger, events *playev
 				admin.Get("/acquisition/settings", h.handleGetSearchSettings)
 				admin.Put("/acquisition/settings", h.handlePutSearchSettings)
 				admin.Get("/wanted/{id}/candidates", h.handleListCandidates)
+				admin.Get("/wanted/{id}/tracks", h.handleWantTracks)
 				admin.Post("/wanted/{id}/search", h.handleSearchWant)
 				admin.Post("/wanted/{id}/grab", h.handleGrabCandidate)
 				admin.Post("/wanted/{id}/block", h.handleBlockCandidate)