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/ui.cattle.io/navlink_v1.json

@@ -0,0 +1,75 @@
+{
+  "$schema": "http://json-schema.org/draft-07/schema#",
+  "properties": {
+    "apiVersion": {
+      "type": "string"
+    },
+    "kind": {
+      "type": "string"
+    },
+    "metadata": {
+      "type": "object"
+    },
+    "spec": {
+      "properties": {
+        "group": {
+          "nullable": true,
+          "type": "string"
+        },
+        "iconSrc": {
+          "nullable": true,
+          "type": "string"
+        },
+        "label": {
+          "nullable": true,
+          "type": "string"
+        },
+        "sideLabel": {
+          "nullable": true,
+          "type": "string"
+        },
+        "target": {
+          "nullable": true,
+          "type": "string"
+        },
+        "toService": {
+          "nullable": true,
+          "properties": {
+            "name": {
+              "nullable": true,
+              "type": "string"
+            },
+            "namespace": {
+              "nullable": true,
+              "type": "string"
+            },
+            "path": {
+              "nullable": true,
+              "type": "string"
+            },
+            "port": {
+              "nullable": true,
+              "x-kubernetes-int-or-string": true
+            },
+            "scheme": {
+              "default": "http",
+              "nullable": true,
+              "type": "string"
+            }
+          },
+          "required": [
+            "name",
+            "namespace"
+          ],
+          "type": "object"
+        },
+        "toURL": {
+          "nullable": true,
+          "type": "string"
+        }
+      },
+      "type": "object"
+    }
+  },
+  "type": "object"
+}