Handle duplicate kinds in listener allowed kinds

Author: fabian4

internal/controller/state/graph/gateway_listener.go

@@ -301,6 +301,9 @@ func getAndValidateListenerSupportedKinds(listener v1.Listener) (
 			}
 			// Use kind as key for uniqueness
 			key := string(kind.Kind)
+			if kind.Group != nil {
+				key = string(*kind.Group) + "/" + key
+			}
 			if _, exists := unique[key]; !exists {
 				unique[key] = struct{}{}
 				supportedKinds = append(supportedKinds, kind)