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

schemas/crd.projectcalico.org/ippool_v1.json

@@ -0,0 +1,74 @@
+{
+  "$schema": "http://json-schema.org/draft-07/schema#",
+  "properties": {
+    "apiVersion": {
+      "type": "string"
+    },
+    "kind": {
+      "type": "string"
+    },
+    "metadata": {
+      "type": "object"
+    },
+    "spec": {
+      "properties": {
+        "allowedUses": {
+          "items": {
+            "type": "string"
+          },
+          "type": "array"
+        },
+        "assignmentMode": {
+          "enum": [
+            "Automatic",
+            "Manual"
+          ],
+          "type": "string"
+        },
+        "blockSize": {
+          "type": "integer"
+        },
+        "cidr": {
+          "type": "string"
+        },
+        "disableBGPExport": {
+          "type": "boolean"
+        },
+        "disabled": {
+          "type": "boolean"
+        },
+        "ipip": {
+          "properties": {
+            "enabled": {
+              "type": "boolean"
+            },
+            "mode": {
+              "type": "string"
+            }
+          },
+          "type": "object"
+        },
+        "ipipMode": {
+          "type": "string"
+        },
+        "nat-outgoing": {
+          "type": "boolean"
+        },
+        "natOutgoing": {
+          "type": "boolean"
+        },
+        "nodeSelector": {
+          "type": "string"
+        },
+        "vxlanMode": {
+          "type": "string"
+        }
+      },
+      "required": [
+        "cidr"
+      ],
+      "type": "object"
+    }
+  },
+  "type": "object"
+}