feat(navigation): add retention metadata to header global

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

packages/navigation/src/integrations/cms/globals/header.ts

@@ -2,6 +2,16 @@ import type { GlobalConfig } from "payload";
 
 export const header: GlobalConfig = {
   slug: "header",
+  custom: {
+    retention: {
+      purgeSchedule: "monthly",
+      postDeletion: {
+        duration: "P90D",
+        trigger: "after-deletion",
+        action: "hard-delete",
+      },
+    },
+  },
   admin: {
     group: "Navigation",
   },