fix docker deployment

docker/.env.example

@@ -13,6 +13,9 @@ ALLOWED_HOSTS=localhost,127.0.0.1,api,frontend,executive.local
 CSRF_TRUSTED_ORIGINS=http://localhost,http://127.0.0.1,http://executive.local
 CORS_ALLOWED_ORIGINS=http://localhost,http://127.0.0.1,http://executive.local
 
+# Host port for the UI (default 80). Use 8080 if :80 is already taken.
+FRONTEND_PORT=80
+
 # Production admin (bootstrap_admin — no demo data)
 BOOTSTRAP_ADMIN_USER=admin
 BOOTSTRAP_ADMIN_PASSWORD=Pr04dm1n