Adds local System Name persistence (trimmed, 1-40) in system_kv, an
injectable sync module with conflict/invalid revert and a pending-sync
flag, a background SystemNameSync worker (retries on boot and on a timer),
and api_client support for PUT /licenses/{key}/system-name plus the
additive systemName field/systemNameStatus on license validation. The
license service sends the stored name and applies the status. Covers
validation, pending retry, and conflict revert with a faked HTTP layer.
NeilClack