- API returns correct trace_ids for each cluster
- Previously, loadClusterResults overwrote trace_ids from clusterTraceIdsMap
- clusterTraceIdsMap uses cluster_id from face_cluster.json (Person_0, etc.)
- But groups may have custom names (Group_aaa), causing key mismatch
- Now only uses clusterTraceIdsMap as fallback when API trace_ids are empty
- Fixes 'Group_aaa 有兩個' display issue caused by lost trace_ids