feat: k8s informer for ServiceAdapter CRDs, bump CI to go1.26

- Add dynamic-client informer to watch ServiceAdapter CRs in-cluster
- Remove typed scheme registration (dynamic client needs no DeepCopy)
- Bump Dockerfile + CI images from golang:1.25 to golang:1.26
  (k8s.io/[email protected] requires go>=1.26)
- Wire informer into main.go startup with graceful fallback

apis/gateway/v1/groupversion_info.go

@@ -21,16 +21,9 @@ package v1
 
 import (
 	"k8s.io/apimachinery/pkg/runtime/schema"
-	"sigs.k8s.io/controller-runtime/pkg/scheme"
 )
 
 var (
-	// GroupVersion is group version used to register these objects
+	// GroupVersion is group version used to register these objects.
 	GroupVersion = schema.GroupVersion{Group: "gateway.riotpiao.com", Version: "v1"}
-
-	// SchemeBuilder is used to add go types to the GroupVersionKind scheme
-	SchemeBuilder = &scheme.Builder{GroupVersion: GroupVersion}
-
-	// AddToScheme adds the types in this group-version to the given scheme.
-	AddToScheme = SchemeBuilder.AddToScheme
 )

apis/gateway/v1/serviceadapter_types.go

@@ -154,6 +154,7 @@ type ServiceAdapterList struct {
 	Items           []ServiceAdapter `json:"items"`
 }
 
-func init() {
-	SchemeBuilder.Register(&ServiceAdapter{}, &ServiceAdapterList{})
-}
+// Note: DeepCopyObject is not generated. The gateway uses the dynamic
+// (unstructured) k8s client, so typed scheme registration is unnecessary.
+// If a typed client is needed later, run controller-gen to generate
+// the DeepCopy methods and re-enable SchemeBuilder.Register here.