Set up a blue-green deployment

Describe and implement a complete blue-green deployment strategy for [App] on [Platform, e.g. AWS ECS, Kubernetes, or Heroku]. Detail the traffic switching mechanism, the health check gates that must pass before traffic is cut over, the one-command rollback procedure in case the new version is unhealthy, and how to keep the idle environment pre-warmed to minimise cold-start latency. Provide all necessary config files and deployment scripts.