The two new NetbirdClientAutoUpdatePayload/NetbirdApiTokenPayload classes
were accidentally inserted between two of SystemConfigUpdate's own
@field_validator methods, which closed that class early — the ssl_mode,
base_domain, npm_api_url, and admin_email validators ended up attached to
NetbirdApiTokenPayload instead, whose fields don't exist. Pydantic raised
PydanticUserError on import, crash-looping the whole appliance container.
Moved the two new classes after all of SystemConfigUpdate's validators.