Two bugs in the backend medications route:
1. Planner /medications/usage had the same +1 phantom consumption bug
that was fixed in the frontend (PR #109). After a stock correction,
effectiveStart was set to max(blisterStart, correctionCutoff) instead
of correctionCutoff + period, causing 1 dose to be immediately
counted as consumed.
2. PUT /medications/:id did not reset stockAdjustment when stock fields
(packCount, blistersPerPack, pillsPerBlister, looseTablets) changed.
If a user edited stock values to correct their inventory, the old
stockAdjustment offset was preserved, resulting in wrong totals.
Added 4 tests covering both scenarios.
Daniel Volz
99bb9c3931