// Validate files: hash exists, no existing labels
	fileIDMap, hashErrors := validateAndMapFiles(database, scannedFiles, input.ClusterID)

	// Validate files: hash exists, linked to dataset, no existing labels
	fileIDMap, hashErrors := validateAndMapFiles(database, scannedFiles, input.ClusterID, input.DatasetID)

// validateAndMapFiles validates files exist by hash and have no existing labels

// validateAndMapFiles validates files exist by hash, are linked to dataset, and have no existing labels

	datasetID string,

		// Verify file is linked to dataset via file_dataset junction table (composite FK)
		var fileLinkedToDataset bool
		err = dbConn.QueryRow(`
			SELECT EXISTS(SELECT 1 FROM file_dataset WHERE file_id = ? AND dataset_id = ?)
		`, fileID, datasetID).Scan(&fileLinkedToDataset)
		if err != nil {
			errors = append(errors, ImportSegmentError{
				File:    filepath.Base(sf.WavPath),
				Stage:   "validation",
				Message: fmt.Sprintf("failed to verify file-dataset link: %v", err),
			})
			continue
		}
		if !fileLinkedToDataset {
			errors = append(errors, ImportSegmentError{
				File:    filepath.Base(sf.WavPath),
				Stage:   "validation",
				Message: fmt.Sprintf("file exists in cluster but is not linked to dataset %s", datasetID),
			})
			continue
		}