feat: a wanted list — follow artists on release-type profiles; requests and re-acquisition become wants (M502 #5520)

Minstrel keeps its own list of what it is to get, keyed by MusicBrainz
release group. A want comes from an approved request, a new release by a
followed artist, or an album whose files went missing, and is held once the
library has a full edition of it.

- Migration 0081: release_type_profiles (Standard seeded: Album, EP,
  Single, studio only), follows, follow_seen_groups and wants.
  lidarr_requests becomes requests with plain *_mbid columns; approved
  album and track requests move onto the wanted list, approved artist
  requests become follows, and the library's album artists start out
  followed. missing_reacquisitions and the retry settings go.
- internal/wanted: follows are checked against MusicBrainz discographies
  daily. The first check sets a baseline, and only releases after it are
  wanted unless the follow asked for what already exists. Profiles filter
  by primary and secondary type, so live recordings stay out unless a
  profile ticks Live.
- internal/requests (was lidarrrequests): approving puts the request on
  the wanted list, and an artist request can be approved on a chosen
  profile. A request completes when its want is held.
- The re-acquisition sweeper wants a missing album back instead of asking
  Lidarr; searching for it is the search schedule's (#5521).
- Web: an admin Wanted page (Wanted, Missing files, Held, Following), a
  follow control on artist pages, a release-type profiles card on
  Integrations, "Approve on a profile" on Requests, and want state on
  Missing files. The artist detail API returns the artist's MBID.
- Android: the request body sends artist_mbid, album_mbid and track_mbid.

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

internal/api/types.go

@@ -102,6 +102,9 @@ type ArtistDetail struct {
 	// Genres carried by this artist's tracks, for quick-jump chips (#367).
 	// Always non-nil at JSON so the client can iterate without a null check.
 	Genres []string `json:"genres"`
+	// MBID is the artist's MusicBrainz id, which following is keyed by
+	// (M502 #5520). Empty when the tags never named one.
+	MBID string `json:"mbid"`
 }
 
 // AlbumDetail is the response body of GET /api/albums/{id}.