set system setting

define a system setting

Upserts one setting in the system_key_value storage: the field pin becomes the document's `label` (spaces stripped, the spelling every reader queries as label.keyword), the value is stored as a string, and description and is_secure are written alongside. An existing setting with the same label is updated rather than duplicated. There is no success or error output; an empty or unwired field does nothing, and a failing write is logged and recorded on the run rather than surfaced on a pin. Writes nothing while simulating.