Fix network alias assignment for DB services

Ensure that the database host alias is only attached to the database
containers themselves, not to dependent application containers. This
avoids DNS collisions where multiple containers expose the same alias
(e.g. 'postgres') on the same network, which led to connection refused
errors in XWiki.

See conversation: https://chatgpt.com/share/68cae4e5-94e4-800f-b291-d2acdb36af21

roles/docker-container/templates/networks.yml.j2

@@ -5,9 +5,11 @@
   application_id in ['svc-db-mariadb','svc-db-postgres']
 %}
       {{ applications | get_app_conf('svc-db-' ~ database_type, 'docker.network') }}:
+{% if application_id in ['svc-db-mariadb','svc-db-postgres'] %}
           aliases:
             - {{ database_host }}
 {% endif %}
+{% endif %}
 {% if applications | get_app_conf(application_id, 'features.ldap', False) and applications | get_app_conf('svc-db-openldap', 'network.docker') %}
       {{ applications | get_app_conf('svc-db-openldap', 'docker.network') }}:
 {% endif %}