Deploy: make LXC installer's cosmetic post-install steps non-fatal

The framework's motd_ssh runs 'chmod -x /etc/update-motd.d/*', which returns 'Operation not permitted' in some unprivileged LXCs. Under the community-scripts ERR trap that aborted an already-successful install right before /usr/bin/update was written. Write the update command first, then run motd_ssh/customize/cleanup best-effort (motd_ssh now guarded like customize already was).

Claude-Session: https://claude.ai/code/session_01Kib2MniVFbD95fkgLgBBnB

deploy/install/metervault-install.sh

@@ -235,9 +235,12 @@ main() {
   systemctl daemon-reload 2>/dev/null || true
   systemctl_enable_now_best_effort metervault
 
-  motd_ssh
-  customize 2>/dev/null || true
+  # Write the important post-install artifact first, then run cosmetic framework steps best-effort.
+  # motd_ssh's `chmod -x /etc/update-motd.d/*` returns "Operation not permitted" in some unprivileged
+  # LXCs; under the framework's ERR trap that would otherwise abort an already-successful install.
   write_update_command
+  motd_ssh 2>/dev/null || true
+  customize 2>/dev/null || true
   cleanup_lxc 2>/dev/null || true
 
   local ip