fix(compose): standardize adminfront port env name

- replace legacy ADMIN_PORT usage with ADMINFRONT_PORT
- add policy test to prevent compose variable drift

docker/staging_pull_compose.template.yaml

@@ -383,7 +383,7 @@ services:
       - APP_ENV=${APP_ENV:-development}
       - API_PROXY_TARGET=http://baron_backend:3000
     ports:
-      - "${ADMIN_PORT:-5173}:5173"
+      - "${ADMINFRONT_PORT:-5173}:5173"
     volumes:
       - ./adminfront:/app
       - /app/node_modules