Generate Ed25519 signing key

[BobWall23]

[BobWall23]

It dawned on me that after we switched direction on passphrase generation, we should have refactored so that instead of requiring an RSA private key in ~/.ssh/id_rsa and reading that key for use as the signing key in the GPG key file, we should have just created a new Ed25519 signing key pair and used that.

Refactor to do this. Figure out how to handle existing files (key files and encrypted files) that don't match the new scheme.