refactor: remove unnecessary frontend_network from compose config

The frontend_network was inherited from upstream repo that included
frontend services, but this demo only deploys backend services
(tracker, proxy, database, monitoring) that all communicate through
the backend_network.

- Remove frontend_network from proxy service networks
- Remove frontend_network definition from networks section
- Simplifies architecture while maintaining all functionality

Author: josecelano

application/compose.yaml

@@ -20,7 +20,6 @@ services:
     container_name: proxy
     restart: unless-stopped
     networks:
-      - frontend_network
       - backend_network
     ports:
       - "80:80"
@@ -133,7 +132,6 @@ services:
       - mysql
 
 networks:
-  frontend_network: {}
   backend_network: {}
 
 volumes: