List SFTP credentials

Example response

{
  "count": 2,
  "results": [
    {
      "id": "ee5d0e45-b098-47bc-8217-e93790243dfa",
      "hostname": "sftp.example.com",
      "port": 22,
      "user": "sftpuser",
      "auth_type": "PASSWORD",
      "key_fingerprint": "SHA256:abc123..."
    }
  ]
}