feat: fetch lyrics during music ingest

backend/src/main/java/com/music/service/IngestService.java

@@ -90,6 +90,8 @@ public class IngestService {
     private final TraditionalFilterService traditionalFilterService;
     private final ConfigService configService;
     private final AudioValidationService audioValidationService;
+    @Autowired(required = false)
+    private LyricsService lyricsService;
 
     /**
      * Spring DI 构造器。
@@ -648,6 +650,9 @@ public class IngestService {
         if (tag != null) {
             extractEmbeddedLyrics(tag, targetDir, trackStr, safeTitle, title, effectiveArtist);
         }
+        if (lyricsService != null) {
+            lyricsService.fetchIfMissing(targetDir.resolve(destFileName), title, effectiveArtist);
+        }
 
         return "ingested";
     }