Add JSON schema generation for kubeconform CRD validation

- ci/generate-schemas.sh generates schemas from CRD manifests and K8s swagger
- Sources: ArgoCD v3.3.2, Gateway API v1.5.1, Kubernetes v1.33.7
- Optionally fetches live cluster CRDs via kubectl when available
- Generated schemas committed to schemas/ for CI use
- Run `make schemas` to regenerate after CRD version bumps
- validate-apps.sh and validate-clusters.sh check local schemas first

Makefile

@@ -6,6 +6,10 @@ build:
 	@mkdir -p manifests/$(filter-out $@,$(MAKECMDGOALS))
 	@kustomize build --enable-helm $(filter-out $@,$(MAKECMDGOALS)) --output manifests/$(filter-out $@,$(MAKECMDGOALS))
 
+# Generate JSON schemas from CRDs and Kubernetes swagger spec (run manually, results committed)
+schemas:
+	@ci/generate-schemas.sh schemas
+
 # kubeconform
 kubeconform:
 	@ci/validate-apps.sh && \