A clear error when the nginx config is missing: on a deploy-app, if the hub did not…

v0.0.3-alpha

A clear error when the nginx config is missing: on a deploy-app, if the hub did not provide the app's child-nginx config (renderedNginx empty — typically a hub↔agent version drift), the agent now fails with an explicit message ("redeploy the hub to align API and agent") before running compose up. Avoids the cryptic Docker error "mounting a directory onto a file" caused by Docker auto-creating the bind source as a directory.