fix(meds): tighten the v1.5 schedule schema invariants

Adds three Zod refines that close gaps the audit surfaced: one-shot
medications now require a startsOn, course windows refuse endsOn
before startsOn, and rolling-cadence schedules cap timesOfDay at one
entry. The wizard's reminders toggle is now part of the create
payload so the user's choice actually ships.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

docs/api/openapi.yaml

@@ -1663,6 +1663,8 @@ components:
           type: integer
           minimum: 1
           maximum: 100
+        notificationsEnabled:
+          type: boolean
         startsOn:
           description: Date the medication course begins (ISO `YYYY-MM-DD`). Anchors RRULE BYDAY / BYMONTHDAY patterns and the
             rolling-interval countdown's first window. NULL = active from creation (the legacy implicit behaviour).