The example only covered `matrix.example.com` and the federation stream,
so people who make the playbook serve the base domain were left without a
proxy host for it. Requests for the `/.well-known/matrix/*` files on the
base domain then never reach Traefik and Nginx Proxy Manager answers with
a 404 error of its own, breaking federation and client discovery.

The nginx example already covers this by listing `example.com` in its
`server_name` directive. Serving the base domain from the Matrix server
is optional though, so the new section says so and points people whose
base domain lives elsewhere to the server delegation documentation.

Also note that a `*.example.com` wildcard certificate does not cover the
base domain itself, which is easy to get wrong when setting this up.

Related to https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/5465

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>