Fix settings import validation

sync/settings.go

@@ -263,7 +263,7 @@ func ImportSettings(r *SettingsImportRequest) (*ImportResult, error) {
 	}
 	if checked < len(settings) {
 		result.ContainsUnknown = true
-		if !r.AllowUnknown {
+		if !r.AllowUnknown && !r.ValidateOnly {
 			return nil, fmt.Errorf("%w: the export contains unknown settings", ErrInvalidImportRequest)
 		}
 	}

sync/util.go

@@ -140,7 +140,7 @@ func parseExport(request *ImportRequest, export any) error {
 	default:
 		// Checksums not supported.
 	}
-	if err != nil && errors.Is(err, filesig.ErrChecksumMissing) {
+	if err != nil && !errors.Is(err, filesig.ErrChecksumMissing) {
 		return fmt.Errorf("failed to verify checksum: %w", err)
 	}