Expose port 8080 on frontend for Traefik routing

Traefik defaults to port 80 when no loadbalancer.server.port label exists;
Frappe nginx listens on 8080. expose: 8080 lets the docker provider pick it.

docker-compose.yml

@@ -174,6 +174,8 @@ services:
   frontend:
     <<: *customizable_image
     platform: linux/amd64
+    expose:
+      - '8080'
     entrypoint: ['bash', '-c']
     command:
       - export FRAPPE_SITE_NAME_HEADER=$$(tr -d '\r\n' < /home/frappe/frappe-bench/sites/currentsite.txt); exec nginx-entrypoint.sh