Add [server].listen_backlog (default 1024) for client-facing listen(2)
queue size; use the same value for metrics HTTP listeners. Hot reload
logs restart-required when this field changes.
- Bump telemt dependency version from 3.3.15 to 3.3.19.
- Add `metrics_listen` option to `config.toml` for specifying a custom address for the metrics endpoint.
- Update `ServerConfig` struct to include `metrics_listen` and adjust logic in `spawn_metrics_if_configured` to prioritize this new option over `metrics_port`.
- Enhance error handling for invalid listen addresses in metrics setup.