make fujin works better with CI/CD

[Tobi-De]

Two issue to resolve for this to work easily

• ssh auth from CI environment
• .env.prod file

[Tobi-De]

env can now be defined directly in the fujin.toml a81376b1cd8d411e358d140618239d3a99357f0f for the ssh auth, I think the simplest solution is just to add a secret in github action with the content of the private key, and before running the deploy command in the action, create the private key file with the content from the secrets at the path fujin expects it

[Tobi-De]

what missing to close this is documenting the process with gh action