fix(proxmox_lxc_provision): wait for container config file before editing it

The proxmox create task can return before pmxcfs has flushed the .conf, so the
first delegated lineinfile hit 'Destination /etc/pve/lxc/<vmid>.conf does not
exist'. Poll for the file with wait_for (up to 30s) before applying idmaps/GPU
config, which continues as soon as it appears rather than eating a fixed sleep.

roles/proxmox_lxc_provision/tasks/edit-config.yml

@@ -6,6 +6,13 @@
 # preserves in place. Each line is keyed on its own exact content, so no comment
 # markers are needed and re-runs stay churn-free.
 
+- name: Wait for the container config file to exist
+  ansible.builtin.wait_for:
+    path: "/etc/pve/lxc/{{ lxc_vmid }}.conf"
+    timeout: 30
+  delegate_to: "{{ proxmox_delegate_host }}"
+  become: true
+
 - name: Configure ID mappings
   ansible.builtin.lineinfile:
     path: "/etc/pve/lxc/{{ lxc_vmid }}.conf"