Migration 000091 creates organization_settings, a key-value store per
organization shaped like outlet_settings, for the loyalty settings that must
be the same in every outlet (point value, exchange rate, transfer limits,
expiry). Until now there was nowhere to keep organization-level settings.
Also creates loyalty_setting_changes, the append-only log of who changed
which loyalty setting from what to what (PRD F2), for both organization and
outlet settings (PC-102).
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
