fix: add container_name for cross-project DNS resolution

roles/docker/templates/listmonk-compose.yml.j2

@@ -1,6 +1,7 @@
 services:
   listmonk:
     image: listmonk/listmonk:latest
+    container_name: listmonk
     restart: unless-stopped
     depends_on:
       db:
@@ -30,6 +31,7 @@ services:
 
   db:
     image: postgres:17-alpine
+    container_name: listmonk_db
     restart: unless-stopped
     environment:
       POSTGRES_USER: listmonk