README:
Updated metadata example to show domain as the only required key.
Documented the bundle's derived_from_domain reactor as the source of
nginx/letsencrypt/monitoring/nftables-input wiring, and the
bundle-defaults source of backup/paths.
nodes/ovh.left4me.py:
- groups: + backup, + left4me, + webserver
- bundles: dropped 'left4me' and 'nftables' (come via groups now;
nftables ships with debian-13).
- metadata: pinned vm/cores=4, vm/threads=8 (4-core HT box) so the
nginx bundle's worker_processes resolves; left4me block reduced to
{'domain': 'left4.me'} — git_url, git_branch, secret_key, and the
nginx/letsencrypt/monitoring/nftables/backup blocks now come from
bundle defaults / the derived_from_domain reactor.
