fix: use traefik-public network to match Netcup Traefik config

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

docker-compose.yml

@@ -8,7 +8,7 @@ services:
         limits:
           memory: 2G
     networks:
-      - proxy
+      - traefik-public
     labels:
       - "traefik.enable=true"
       - "traefik.http.routers.mermaid-animator.rule=Host(`mermaid.jeffemmett.com`)"
@@ -17,5 +17,5 @@ services:
       - "traefik.http.services.mermaid-animator.loadbalancer.server.port=3999"
 
 networks:
-  proxy:
+  traefik-public:
     external: true