Set up remote deployment for new server (GitHub Actions)

In order to Stage a PR with GitHub Actions, we need to prepare the new staging server.

1. Run playbook setup_remote_deployment.yml for the staging server.

Until this issue is done, we also need to:

2. Update GitHub Secret DEPLOYMENT_HOSTS to include known_hosts entries for all staging servers, including this new one. (check BitWarden for the current value, and ensure it's updated)
3. Authorise 'semaphore' deployment key for user ofn-deploy (see https://github.com/openfoodfoundation/ofn-install/issues/941#issuecomment-2373076883 )