chore: Remove Traefik from deploy stack (using Nginx)

- Remove Traefik network and labels from docker-compose
- Remove redundant docker-compose.simple.yml
- Remove HUB_DOMAIN from .env.example
- Remove traefik network creation from setup.sh

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

deploy/.env.example

@@ -7,7 +7,6 @@
 
 # Hub public URL (used for auth callbacks and runner communication)
 HUB_URL=https://hub.yourdomain.com
-HUB_DOMAIN=hub.yourdomain.com
 
 # Database password (generate a strong random password)
 POSTGRES_PASSWORD=CHANGE_ME_STRONG_PASSWORD_HERE