feat: import library from media root and stream tracks

Add a filesystem scanner that ingests supported audio files from MEDIA_ROOT into SQLite using embedded tags with filename fallbacks. Wire startup scanning, manual rescan, and authenticated audio streaming into the backend, then connect the web player to the real stream endpoint.

cmd/server/main.go

@@ -12,6 +12,7 @@ import (
 	"github.com/benya/temporserv/internal/config"
 	"github.com/benya/temporserv/internal/db"
 	"github.com/benya/temporserv/internal/httpapi"
+	"github.com/benya/temporserv/internal/scanner"
 )
 
 func main() {
@@ -32,7 +33,16 @@ func main() {
 		log.Fatalf("database seed failed: %v", err)
 	}
 
-	handler := httpapi.NewRouter(cfg, database)
+	scanService := scanner.NewService(database, cfg.MediaRoot)
+	if scanService.HasMediaFiles() {
+		if result, err := scanService.Scan(ctx); err != nil {
+			log.Printf("startup scan failed: %v", err)
+		} else {
+			log.Printf("startup scan completed: artists=%d albums=%d tracks=%d", result.Artists, result.Albums, result.Tracks)
+		}
+	}
+
+	handler := httpapi.NewRouter(cfg, database, scanService)
 
 	server := &http.Server{
 		Addr:              cfg.Address(),