feat(medications): persist a per-dose configurable intake window

Add `doseWindows` (Json?) to MedicationSchedule: a nullable array of
`{ timeOfDay, start, end }` HH:mm triples naming an explicit on-time
range for a dose time (e.g. 07:00–09:00). A time with no entry keeps the
symmetric ±1h default; a NULL column leaves every slot on the default
derivation, so the migration is additive and changes no existing
behaviour. Migration 0137 adds the column with no backfill.

prisma/migrations/0137_v11518_dose_windows/migration.sql

@@ -0,0 +1,18 @@
+-- v1.15.18 — per-dose configurable intake WINDOW.
+--
+-- Marc's "07:00–09:00" lever: a dose time can carry an explicit on-time RANGE
+-- instead of the symmetric ±1h default the band minter derives. The column is
+-- a nullable JSON array of `{ timeOfDay, start, end }` HH:mm triples, one per
+-- dose time the user gave an explicit window for, e.g.
+--   [{ "timeOfDay": "07:00", "start": "07:00", "end": "09:00" }]
+--
+-- The band minter reads it to build the on-time band from `[start, end]` for
+-- the matching `timeOfDay`; a time with no entry keeps the default ±1h
+-- derivation, and a NULL column leaves every slot on the default (unchanged
+-- behaviour). The late tail stays cadence-derived.
+--
+-- Additive + non-destructive: a new nullable column with no backfill. Existing
+-- rows read NULL and behave exactly as before; the iOS contract gains an
+-- optional field.
+ALTER TABLE "medication_schedules"
+  ADD COLUMN "dose_windows" JSONB;

prisma/schema.prisma

@@ -1388,6 +1388,16 @@ model MedicationSchedule {
   /// v1.7.0 — cyclic "off" weeks. Only meaningful when
   /// `scheduleType = CYCLIC`.
   cyclicOffWeeks Int? @map("cyclic_off_weeks")
+  /// v1.15.18 — per-dose on-time intake WINDOW (the configurable lever).
+  /// A JSON array of `{ timeOfDay, start, end }` HH:mm triples, one per
+  /// dose time the user wants an explicit range for (e.g.
+  /// `[{ "timeOfDay": "07:00", "start": "07:00", "end": "09:00" }]`).
+  /// The band minter reads this to build the on-time band from the
+  /// explicit `[start, end]` range for the matching `timeOfDay`; a
+  /// `timeOfDay` with no entry falls back to the symmetric ±1h default.
+  /// The late tail stays cadence-derived. NULL = every slot uses the
+  /// default derivation (unchanged behaviour). Additive + iOS-safe.
+  doseWindows  Json? @map("dose_windows")
 
   medication       Medication                @relation(fields: [medicationId], references: [id], onDelete: Cascade)
   telegramMessages TelegramReminderMessage[]