Variables that map to nested YAML config properties should follow the pattern:
matrix_<component>_<configPath>_<nestedProperty>

For ircService.mediaProxy.*, we now use:
- matrix_appservice_irc_ircService_mediaProxy_bindPort
- matrix_appservice_irc_ircService_mediaProxy_publicUrl_hostname
- matrix_appservice_irc_ircService_mediaProxy_publicUrl_pathPrefix

This follows the existing pattern used by matrix_appservice_irc_ircService_servers
and similar variables in other roles (e.g., matrix_hookshot_github_defaultOptions_*).

Also renamed the Traefik path prefix variable to include 'media_proxy' for clarity:
- matrix_appservice_irc_container_labels_media_proxy_traefik_path_prefix