Write a GitHub Actions workflow to implement a release train with scheduled promotion across environments

Steps

1. Define a workflow triggered by schedule (cron syntax) for automatic promotion windows (e.g., every Tuesday at 10:00 UTC) and by workflow_dispatch for manual promotion.
2. Use a matrix strategy with a JSON array of environment objects (e.g., [{name: staging, cluster: stg}, {name: production, cluster: prod}]) to fan out deployment steps across environments in a controlled sequence.
3. Use needs to enforce ordering between matrix jobs so staging must succeed before production is attempted, creating a linear promotion chain within a single workflow run.
4. Gate production promotion with a GitHub environment protection rule (required reviewers or a deployment timer) on the production environment so the matrix job pauses for approval.
5. Pass the image tag or artifact version as a workflow input (for workflow_dispatch) or derive it from a previous release job that publishes the version to a workflow output.
6. Log the promotion results for each environment in the GitHub deployment API (create deployment + deployment status) to maintain an auditable promotion history per environment.