Make generated Express apps production-ready

[theinfosecguy]

Problem & Solution Overview

Generated Express apps are now production-ready:

• Load .env via dotenv, and the mongoose config uses MONGODB_URI (falling back to a local DB).
• A /health endpoint returning { status: 'ok' }.
• Centralized error-handling middleware.
• Graceful shutdown on SIGINT/SIGTERM (closes the server, and the Mongo connection for --db).
• Binds to 0.0.0.0 so it works in Docker.
• start, dev, and test scripts.
• The app is exported (and only listens when run directly), so it ships with a basic integration test (node --test + supertest) hitting /health and /.

These apply to the Express templates only; Node apps are unchanged.

Testing Done

• npm test: 231 passing (8 new integration tests covering the health endpoint, dotenv/export, 0.0.0.0 + signal handlers, error middleware, the start/dev/test scripts + supertest, the generated test file, MONGODB_URI, and that node apps don't get the express scaffolding).
• npm run test:package (release smoke): from the installed tarball, generates an Express app, installs it, runs the generated app's own npm test, boots it, asserts 200 on / and /health, and confirms a clean exit-0 shutdown on SIGTERM.
• Verified the full lifecycle locally end to end (install, generated npm test 2/2, /health 200, graceful SIGTERM).