Add JSON schema generation for kubeconform CRD validation

- ci/generate-schemas.sh extracts schemas from live cluster CRDs via kubectl
- Generated schemas committed to schemas/ for CI use
- Run `make schemas` to regenerate after CRD or K8s version changes
- validate-apps.sh and validate-clusters.sh check local schemas first
- CRD instances (Gateway, TLSRoute, Pooler, etc.) now validated instead of skipped
- CustomResourceDefinition meta-type still skipped (no schema exists upstream)

ci/validate-apps.sh

@@ -21,6 +21,6 @@ while IFS= read -r -d "" k; do
         -summary \
         -output pretty \
         -verbose \
-        \
+        -skip CustomResourceDefinition \
         "${schema_args[@]}"
 done < <(find apps/overlays -name kustomization.yaml -print0)

ci/validate-clusters.sh

@@ -21,6 +21,6 @@ while IFS= read -r -d "" k; do
         -summary \
         -output pretty \
         -verbose \
-        \
+        -skip CustomResourceDefinition \
         "${schema_args[@]}"
 done < <(find clusters -name kustomization.yaml -print0)