feat: integrate musicfs for post-download metadata enrichment

- Add internal/musicfs package: gRPC client, TriggerRescan (stream consumer), EnrichFiles (BatchUpdateMetadata), DeriveSubdir helper
- Add MusicFS config section (enabled, endpoint, origin_id, origin_root, timeout)
- Wire MusicFSClient into PollDownloadWorker: on download completion, trigger scoped rescan then push enriched metadata
- Fix album auto-persist in monitor workflow: persist artist+album from metadata-agregator before saving torrent/download
- Add filterByActiveSeeders: skip torrents where magnet resolution found 0 real active seeders
- Add musicfs proto to buf.gen.yaml inputs
- Enricher only sends non-empty fields to avoid overwriting existing file tag data with empty values

internal/workers/poll_download.go

@@ -10,6 +10,8 @@ import (
 
 	"homelab.lan/music-agregator/internal/analysis"
 	"homelab.lan/music-agregator/internal/database"
+	"homelab.lan/music-agregator/internal/metadata"
+	"homelab.lan/music-agregator/internal/musicfs"
 	"homelab.lan/music-agregator/internal/torrent"
 )
 
@@ -23,14 +25,18 @@ func (PollDownloadArgs) Kind() string { return "poll_download" }
 
 type PollDownloadWorker struct {
 	river.WorkerDefaults[PollDownloadArgs]
-	TorrentClient torrent.TorrentClient
-	Downloads     *database.DownloadRepository
-	DownloadFiles *database.DownloadFileRepository
-	AlbumReleases *database.AlbumReleaseRepository
-	TrackReleases *database.TrackReleaseRepository
-	RiverClient   *river.Client[pgx.Tx]
-	PathMapper    *torrent.PathMapper
-	Analyzer      *analysis.ReleaseAnalyzer
+	TorrentClient    torrent.TorrentClient
+	Downloads        *database.DownloadRepository
+	DownloadFiles    *database.DownloadFileRepository
+	AlbumReleases    *database.AlbumReleaseRepository
+	TrackReleases    *database.TrackReleaseRepository
+	RiverClient      *river.Client[pgx.Tx]
+	PathMapper       *torrent.PathMapper
+	Analyzer         *analysis.ReleaseAnalyzer
+	MusicFSClient    *musicfs.Client
+	MusicFSOriginID  string
+	MusicFSOriginRoot string
+	MetadataService  *metadata.MetadataService
 }
 
 func (w *PollDownloadWorker) Work(ctx context.Context, job *river.Job[PollDownloadArgs]) error {
@@ -117,9 +123,60 @@ func (w *PollDownloadWorker) onCompleted(ctx context.Context, args PollDownloadA
 		}
 	}
 
+	if w.MusicFSClient != nil {
+		w.syncAndEnrichMusicFS(ctx, args, contentPath)
+	}
+
 	return nil
 }
 
+func (w *PollDownloadWorker) syncAndEnrichMusicFS(ctx context.Context, args PollDownloadArgs, contentPath string) {
+	subdir := musicfs.DeriveSubdir(w.MusicFSOriginRoot, contentPath)
+
+	result, err := w.MusicFSClient.TriggerRescan(ctx, w.MusicFSOriginID, subdir)
+	if err != nil {
+		log.Warn().Err(err).Msg("musicfs rescan failed")
+		return
+	}
+
+	log.Info().
+		Int("new_files", len(result.NewFiles)).
+		Uint64("bytes_synced", result.BytesSynced).
+		Msg("musicfs rescan complete")
+
+	if len(result.NewFiles) == 0 {
+		return
+	}
+
+	download, err := w.Downloads.GetByID(ctx, args.DownloadID)
+	if err != nil {
+		log.Warn().Err(err).Msg("failed to get download for enrichment")
+		return
+	}
+
+	if w.MetadataService == nil {
+		log.Warn().Msg("no metadata service configured, skipping enrichment")
+		return
+	}
+
+	album, err := w.MetadataService.GetAlbumByID(ctx, download.AlbumID)
+	if err != nil {
+		log.Warn().Err(err).Str("album_id", download.AlbumID).Msg("failed to get album for enrichment")
+		return
+	}
+
+	albumMeta, err := w.MetadataService.GetAlbum(ctx, album.ExternalID)
+	if err != nil {
+		log.Warn().Err(err).Str("external_id", album.ExternalID).Msg("failed to get album metadata for enrichment")
+		return
+	}
+
+	err = w.MusicFSClient.EnrichFiles(ctx, result.NewFiles, albumMeta)
+	if err != nil {
+		log.Warn().Err(err).Msg("musicfs enrichment failed")
+	}
+}
+
 func (w *PollDownloadWorker) reschedule(ctx context.Context, args PollDownloadArgs) error {
 	if w.RiverClient == nil {
 		log.Warn().Str("download_id", args.DownloadID).Msg("no river client, cannot reschedule poll_download")