- Trigger deploy workflow on push to `develop` branch (in addition to `master`)
- Add `staging-latest` Docker image tag for develop branch builds
- Add `rollback-staging` job: auto-reverts to previous images on smoke test failure
- Add Slack success notification for staging deploys (previously only failure was notified)
- Record pre-deploy image digests for rollback capability
- Update deployment docs with CI/CD pipeline details, rollback procedures, and required secrets
Co-Authored-By: Paperclip <noreply@paperclip.ing>