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)

schemas/groupsnapshot.storage.k8s.io/volumegroupsnapshotclass_v1beta2.json

@@ -0,0 +1,53 @@
+{
+  "$schema": "http://json-schema.org/draft-07/schema#",
+  "properties": {
+    "apiVersion": {
+      "type": "string"
+    },
+    "deletionPolicy": {
+      "enum": [
+        "Delete",
+        "Retain"
+      ],
+      "type": "string",
+      "x-kubernetes-validations": [
+        {
+          "message": "deletionPolicy is immutable once set",
+          "rule": "self == oldSelf"
+        }
+      ]
+    },
+    "driver": {
+      "type": "string",
+      "x-kubernetes-validations": [
+        {
+          "message": "driver is immutable once set",
+          "rule": "self == oldSelf"
+        }
+      ]
+    },
+    "kind": {
+      "type": "string"
+    },
+    "metadata": {
+      "type": "object"
+    },
+    "parameters": {
+      "additionalProperties": {
+        "type": "string"
+      },
+      "type": "object",
+      "x-kubernetes-validations": [
+        {
+          "message": "parameters are immutable once set",
+          "rule": "self == oldSelf"
+        }
+      ]
+    }
+  },
+  "required": [
+    "deletionPolicy",
+    "driver"
+  ],
+  "type": "object"
+}