fix: honor libvirt network config, preserve DHCP DNS with search-only NM config, and exact-match Xen VM names

roles/system_check/tasks/main.yml

@@ -101,7 +101,11 @@
       when: hypervisor_type == "xen"
       ansible.builtin.assert:
         that:
-          - hostname not in system_check_xen_existing_vms.stdout | default('')
+          - >-
+            not (
+              system_check_xen_existing_vms.stdout | default('')
+              is search('(?m)^' ~ (hostname | ansible.builtin.regex_escape) ~ '\\s+\\d+\\s')
+            )
         fail_msg: |
           VM {{ hostname }} already exists on Xen hypervisor.
           To avoid data loss, the playbook will not overwrite or delete existing VMs.