Add 1-min TTL caching to CheckQuotaHandler (previously uncached, hitting
3 DB queries per guarded request). Add cache invalidation to
MeterUsageHandler and UpgradeSubscriptionHandler so quota caches stay
fresh after usage metering and plan changes. Increase search results TTL
from 1min to 2min per spec. Add market cache invalidation on listing
creation to keep district stats and market reports consistent.
Co-Authored-By: Paperclip <noreply@paperclip.ing>
05651ba4c3