fix: use compose_network for asciinema stack

Changed network reference from ${NETWORK_NAME} variable to hardcoded
compose_network to fix deployment issue where arty doesn't export
environment variables to docker compose.

Changes:
- Network: ${NETWORK_NAME} → compose_network
- Removed external network declaration (inherited from root)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

asciinema/compose.yaml

@@ -4,7 +4,7 @@ services:
     container_name: ${ASCIINEMA_COMPOSE_PROJECT_NAME}_app
     restart: unless-stopped
     networks:
-      - ${NETWORK_NAME}
+      - compose_network
     volumes:
       - asciinema_data:/var/opt/asciinema
       - ./theme/custom.css:/app/assets/css/custom.css:ro
@@ -44,7 +44,3 @@ services:
 volumes:
   asciinema_data:
     name: ${ASCIINEMA_COMPOSE_PROJECT_NAME}_data
-
-networks:
-  ${NETWORK_NAME}:
-    external: true