feat: duplicates resolve themselves without Lidarr (M502 #5517)

Lidarr is off, and with it the resolver had stopped merging: it only
merged when Lidarr had said which copies it mapped. Minstrel is now the
only program writing the library, so the rule is about the copies:

- A song held twice on one album: the extra copies merge into the one
  whose tags fit best (then lossless, larger, older).
- Across releases or under another title: when every copy but one is a
  video rip (held back, or named like one and not marked fine), the rips
  merge into the one that is not.
- Clean copies on different releases are linked as one song, as before.
- Anything else waits for the operator.

Gone with Lidarr: release switches and their settle window, the
unmapped-file read, the rip search, the merge guard and its 409/503,
lidarr.Client's release methods, and duplicate_group_members.lidarr_state
(migration 0078). The duplicates page drops the per-copy Lidarr badge
and the blocked-merge notice; past release changes stay in its history.

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

internal/api/admin_duplicates_test.go

@@ -65,27 +65,26 @@ func TestFoldDuplicateGroups(t *testing.T) {
 }
 
 // M498: the proposal shown beside a group follows the resolver's rule. The copy
-// Lidarr tracks is proposed even when the other is lossless, because removing
-// the tracked one would make Lidarr download it again.
-func TestFoldDuplicateGroups_ProposesTheCopyLidarrTracks(t *testing.T) {
+// whose tags fit the album is proposed even when the other is lossless.
+func TestFoldDuplicateGroups_ProposesTheCopyWhoseTagsFit(t *testing.T) {
 	at := time.Date(2025, 1, 1, 0, 0, 0, 0, time.UTC)
-	tracked, unmapped := "tracked", "unmapped"
 	class := "same_release"
+	three := int32(3)
 	rows := []dbq.ListPendingDuplicateGroupMembersRow{
 		{GroupID: dupUUID(3), Tier: "acoustic", DetectedAt: dupTS(at), TrackID: dupUUID(30), Class: &class,
-			Title: "Song", FileFormat: "flac", FileSize: 30_000_000, AddedAt: dupTS(at), LidarrState: &unmapped},
+			Title: "Song", FileFormat: "flac", FileSize: 30_000_000, AddedAt: dupTS(at)},
 		{GroupID: dupUUID(3), Tier: "acoustic", DetectedAt: dupTS(at), TrackID: dupUUID(31), Class: &class,
-			Title: "Song", FileFormat: "mp3", FileSize: 9_000_000, AddedAt: dupTS(at), LidarrState: &tracked},
+			Title: "Song", FileFormat: "mp3", FileSize: 9_000_000, AddedAt: dupTS(at), TrackNumber: &three, HasMbid: true},
 	}
 	got := foldDuplicateGroups(rows)
 	if len(got) != 1 {
 		t.Fatalf("folded %d groups, want 1", len(got))
 	}
 	g := got[0]
-	if g.SurvivorTrackID != uuidToString(dupUUID(31)) || g.SurvivorReason != "the copy Lidarr tracks" {
-		t.Errorf("survivor = (%s, %q), want the tracked mp3", g.SurvivorTrackID, g.SurvivorReason)
+	if g.SurvivorTrackID != uuidToString(dupUUID(31)) || g.SurvivorReason != "tags fit the album" {
+		t.Errorf("survivor = (%s, %q), want the tagged mp3", g.SurvivorTrackID, g.SurvivorReason)
 	}
-	if g.Class == nil || *g.Class != "same_release" || g.Members[1].LidarrState == nil || *g.Members[1].LidarrState != "tracked" {
-		t.Errorf("class or lidarr state not carried: %+v", g)
+	if g.Class == nil || *g.Class != "same_release" {
+		t.Errorf("class not carried: %+v", g)
 	}
 }