fix: replace client-go informer with REST loader, drop k8s deps

Informer cache sync timed out due to transient 429 from API server.
REST loader does one GET + retry, polls every 30s. Zero new deps.
go.mod back to 1.25.4, CI back to golang:1.25-bookworm.

apis/gateway/v1/groupversion_info.go

@@ -1,29 +1,13 @@
-/*
-Copyright 2026.
-
-Licensed under the Apache License, Version 2.0 (the "License");
-you may not use this file except in compliance with the License.
-You may obtain a copy of the License at
-
-    http://www.apache.org/licenses/LICENSE-2.0
-
-Unless required by applicable law or agreed to in writing, software
-distributed under the License is distributed on an "AS IS" BASIS,
-WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-See the License for the specific language governing permissions and
-limitations under the License.
-*/
-
-// Package v1 contains API Schema definitions for the gateway v1 API group
+// Package v1 contains API Schema definitions for the gateway v1 API group.
+// These types document the CRD shape; the gateway itself uses the dynamic
+// REST loader (no typed client, no scheme registration).
+//
 // +kubebuilder:object:generate=true
 // +groupName=gateway.riotpiao.com
 package v1
 
-import (
-	"k8s.io/apimachinery/pkg/runtime/schema"
-)
-
-var (
-	// GroupVersion is group version used to register these objects.
-	GroupVersion = schema.GroupVersion{Group: "gateway.riotpiao.com", Version: "v1"}
+// GroupVersion constants for the CRD.
+const (
+	Group   = "gateway.riotpiao.com"
+	Version = "v1"
 )