Error Response Format

{
  "error": {
    "code": "VALIDATION_ERROR",
    "message": "The request body contains invalid parameters.",
    "details": [
      {
        "field": "email",
        "issue": "Must be a valid email address",
        "value": "not-an-email"
      }
    ],
    "request_id": "req_abc123xyz",
    "docs_url": "https://docs.nexus.dev/errors/VALIDATION_ERROR"
  }
}