Bridges based on bridgev2 no longer expose a metrics endpoint, so the
playbook was publishing a Traefik route which could only ever yield an
HTTP 502.

Related to https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/5487

The variable was defined, but the configuration template hardcoded the
command prefix, so changing the variable had no effect.

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

Part of adopting a uniform naming policy for bridge variables,
where the variable prefix matches the role directory name.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>