feat(api): SHA-256 and Chromaprint fingerprints for the library (M5.5)

A background Fingerprinter runs after every scan and at startup, one file
at a time, filling media_files.sha256 and track_fingerprints (fpcalc raw,
first 120 s). Without fpcalc only SHA-256 is computed and files stay
queued for Chromaprint. Changing a file's content resets its prints.
Similarity() compares raw prints with a ±80-point alignment search; it is
the basis for duplicate detection in the upload queue.

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

services/api/cmd/api/main.go

@@ -106,11 +106,21 @@ func run() error {
 		log.Warn("STREAM_SIGNING_KEY is not set: cover and stream links will break on restart")
 	}
 	covers := library.NewCovers(libStore, libSvc, cfg.FFmpegPath, filepath.Join(cfg.CacheDir, "covers"), log)
+	fingerprints := library.NewFingerprinter(libStore, library.FPCalc{Bin: cfg.FPCalcPath, Timeout: time.Minute},
+		func(ctx context.Context, sourceID uuid.UUID) (string, error) {
+			src, err := libStore.GetSource(ctx, sourceID)
+			if err != nil {
+				return "", err
+			}
+			return libSvc.Root(src)
+		}, log)
 	scanner.AfterScan = func(ctx context.Context) {
 		covers.Run(ctx)
 		indexer.Trigger()
+		fingerprints.Trigger(ctx)
 	}
 	go covers.Run(ctx) // альбомы, оставшиеся без обложки с прошлого запуска
+	fingerprints.Trigger(ctx)
 
 	concurrency := cfg.TranscodeConcurrency
 	if concurrency <= 0 {