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.go

@@ -14,7 +14,6 @@ import (
 	"git.fabledsword.com/bvandeusen/minstrel/internal/audit"
 	"git.fabledsword.com/bvandeusen/minstrel/internal/db/dbq"
 	"git.fabledsword.com/bvandeusen/minstrel/internal/library"
-	"git.fabledsword.com/bvandeusen/minstrel/internal/tracks"
 )
 
 // duplicateMemberView is one copy in a proposed duplicate group. LikeCount and
@@ -33,12 +32,8 @@ type duplicateMemberView struct {
 	AddedAt     string `json:"added_at"`
 	LikeCount   int64  `json:"like_count"`
 	PlayCount   int64  `json:"play_count"`
-	// LidarrState is Lidarr's view of the file as of the resolver's last pass
-	// (M498): "tracked" (mapped to a track, so it cannot be removed without
-	// Lidarr downloading it again), "unmapped", or null when not asked.
-	LidarrState *string `json:"lidarr_state"`
-	DiscNumber  *int32  `json:"disc_number"`
-	TrackNumber *int32  `json:"track_number"`
+	DiscNumber  *int32 `json:"disc_number"`
+	TrackNumber *int32 `json:"track_number"`
 }
 
 // duplicateGroupView is one proposal. SurvivorTrackID and SurvivorReason are
@@ -291,14 +286,12 @@ func foldDuplicateGroups(rows []dbq.ListPendingDuplicateGroupMembersRow) []dupli
 			AddedAt:     formatTimestamp(row.AddedAt),
 			LikeCount:   row.LikeCount,
 			PlayCount:   row.PlayCount,
-			LidarrState: row.LidarrState,
 			DiscNumber:  row.DiscNumber,
 			TrackNumber: row.TrackNumber,
 		})
 		candidates[n] = append(candidates[n], library.SurvivorCandidate{
 			TrackID: trackID, FileFormat: row.FileFormat, FileSize: row.FileSize, AddedAt: row.AddedAt.Time,
-			LidarrTracked: row.LidarrState != nil && *row.LidarrState == "tracked",
-			TagFit:        library.TagFitScore(row.TrackNumber != nil, row.PositionClash, row.FilePath, row.HasMbid),
+			TagFit: library.TagFitScore(row.TrackNumber != nil, row.PositionClash, row.FilePath, row.HasMbid),
 		})
 	}
 	for i := range groups {
@@ -398,10 +391,6 @@ const mergeRequestBodyLimit = 1 << 16
 // Errors:
 //   - 409 library_not_writable / 500 file_delete_failed when a file could not be
 //     removed — nothing was changed (fileRemoveAPIError)
-//   - 409 copy_tracked_by_lidarr when a copy to remove is one Lidarr maps to a
-//     track: removing it would make Lidarr download it again (M498)
-//   - 503 lidarr_unavailable when Lidarr is on but did not answer, so that
-//     cannot be checked
 //   - 404 duplicate_group_not_pending when the group was already resolved
 //   - 400 survivor_not_in_group, invalid_id, invalid_body
 func (h *handlers) handleMergeDuplicateGroup(w http.ResponseWriter, r *http.Request) {
@@ -439,11 +428,6 @@ func (h *handlers) handleMergeDuplicateGroup(w http.ResponseWriter, r *http.Requ
 			writeAdminJSONErr(w, http.StatusNotFound, "duplicate_group_not_pending")
 		case errors.Is(err, library.ErrSurvivorNotInGroup):
 			writeAdminJSONErr(w, http.StatusBadRequest, "survivor_not_in_group")
-		case errors.Is(err, library.ErrCopyTrackedByLidarr):
-			writeAdminJSONErr(w, http.StatusConflict, "copy_tracked_by_lidarr")
-		case errors.Is(err, tracks.ErrLidarrUnavailable):
-			h.logger.Warn("admin: merge duplicate group: lidarr unavailable", "group_id", uuidToString(groupID), "err", err)
-			writeAdminJSONErr(w, http.StatusServiceUnavailable, "lidarr_unavailable")
 		default:
 			h.logger.Error("admin: merge duplicate group", "group_id", uuidToString(groupID), "err", err)
 			writeAdminJSONErr(w, http.StatusInternalServerError, "server_error")