List secret groups

{
  "groups": [
    {
      "id": "sg_abc123",
      "name": "legal-apis",
      "description": "API keys for legal research services",
      "createdAt": "2024-01-15T10:30:00Z",
      "updatedAt": "2024-01-15T10:30:00Z"
    },
    {
      "id": "sg_def456",
      "name": "database-creds",
      "description": "Database connection credentials",
      "createdAt": "2024-01-10T14:20:00Z",
      "updatedAt": "2024-01-12T09:15:00Z"
    }
  ]
}