Add Proxmox helper script detection to preflight

roles/preflight/tasks/main.yml

@@ -79,3 +79,13 @@
 - name: Preflight complete
   ansible.builtin.debug:
     msg: "Preflight passed for {{ inventory_hostname }} — proceeding with maintenance"
+
+- name: Check for Proxmox helper script marker
+  ansible.builtin.stat:
+    path: /usr/bin/update
+  register: helper_script_marker
+
+- name: Log helper script detection
+  ansible.builtin.debug:
+    msg: "INFO: This LXC was deployed via Proxmox helper script — built-in update script detected at /usr/bin/update. Ansible will manage updates instead."
+  when: helper_script_marker.stat.exists