fix: add traefik.docker.network label to fix staging routing

Traefik was picking the wrong Docker network (_default) for the staging
api container, causing requests to hang. Force it to use the coolify
network which is shared with the Traefik proxy.

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

docker-compose.coolify.yml

@@ -61,6 +61,8 @@ services:
       timeout: 5s
       retries: 5
       start_period: 30s
+    labels:
+      - "traefik.docker.network=coolify"
     expose:
       - "4000"
     networks: