extendUserTier called setUserTier, which unconditionally zeroed
monthly_consumed and re-anchored the cycle. A user who renewed mid-cycle
(or a webhook double-firing across a restart) got their full monthly
allotment back for free. The monthly cycle already rolls on its own
anniversary via ensureRenewalRollover, so renewal must not reset it. Add
resetCycle to setUserTier (default true, preserving operator-grant
behavior); extendUserTier passes false for an in-force subscription and
true only for a brand-new or lapsed one. Add regression tests.
Keysat