feat(library): AcoustID lookup worker fills the MBIDs tags leave empty (M401 #3920 #3921)

Migration 0069 adds tracks.mbid_source (tag | acoustid), a lookup state per
track (matched | ambiguous | no_match | failed) and the acoustid_settings
row (off, no key, min score 0.85).

The file's tag outranks a lookup (D4). UpsertTrack keeps a looked-up id
through a re-read that finds no tag id and replaces it as soon as one
appears. SetTrackMbidFromAcoustID refuses to write over a tag id.

The worker fingerprints each untagged track with fpcalc's compressed
print, looks it up and writes an id only when D5 settles it: one
recording at or above the threshold, or one left after matching title and
length. Ambiguous and no-match results write nothing. A key AcoustID
refuses, or the service being unreachable, stops the pass and is reported
in the worker's status. It never counts as a verdict on a track.

A changed file drops its lookup in the scan. The re-lookup takes back an
id that no longer matches.

Admin API: GET /api/admin/library/acoustid (settings, status, coverage by
source), PUT …/acoustid-settings (write-only key), POST …/acoustid/run,
GET …/acoustid/unsettled.

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

internal/db/dbq/models.go

@@ -187,6 +187,14 @@ func (ns NullLidarrRequestStatus) Value() (driver.Value, error) {
 	return string(ns.LidarrRequestStatus), nil
 }
 
+type AcoustidSetting struct {
+	ID        bool
+	Enabled   bool
+	ApiKey    *string
+	MinScore  float32
+	UpdatedAt pgtype.Timestamptz
+}
+
 type Album struct {
 	ID                     pgtype.UUID
 	Title                  string
@@ -720,6 +728,17 @@ type Track struct {
 	TagSourcesVersion int32
 	TagReadVersion    int16
 	MissingSince      pgtype.Timestamptz
+	MbidSource        *string
+}
+
+type TrackAcoustidLookup struct {
+	TrackID       pgtype.UUID
+	State         string
+	BestScore     *float32
+	Candidates    int32
+	RecordingMbid *string
+	Detail        *string
+	LookedUpAt    pgtype.Timestamptz
 }
 
 type TrackFingerprint struct {