chore(schema): deploy medication_schedules.days_of_week column

The schema declared `MedicationSchedule.daysOfWeek` (mapped to
`days_of_week`) but no migration ever created the column. Code
paths in src/components/medications/*, src/app/api/medications/*,
src/app/api/admin/notifications/reminder-check/*, and the
achievements route all reference it via the comma-separated
"0,1,3,5" recurrence string.

Pre-v1.4.23 deploys silently survived because the existing query
sites only selected the column on SELECT — Postgres would have
failed loudly the moment a user actually saved a non-default
recurrence string via the medication form.

Migration `0039_medication_schedule_days_of_week` adds the column
nullable, default NULL. NULL means "daily" — `parseScheduleRecurrence(null)`
already returns the all-7-days set, so existing rows get the correct
semantics without backfill.

H5 decision rationale: deploy (Option A) over drop (Option B). The
field is referenced by 9 source files across 4 user-visible surfaces
(medication form, card, intake list, reminder dispatcher). Removing
it would force a UI rewrite of the recurrence picker and break
existing test fixtures. Deploying matches the schema's stated intent
and unblocks the v1.4.21 senior-dev review's MED-5 flag.

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

prisma/migrations/0039_medication_schedule_days_of_week/migration.sql

@@ -0,0 +1,17 @@
+-- v1.4.23 H5 — schema drift fix for medication_schedules.days_of_week.
+--
+-- Up to v1.4.22 the column was declared in `schema.prisma` but never
+-- migrated. Code paths in src/components/medications/*,
+-- src/app/api/medications/*, src/app/api/admin/notifications/reminder-check/*
+-- and src/app/api/gamification/achievements/route.ts all reference the
+-- field. Pre-v1.4.23 deploys silently relied on Prisma's selecting
+-- a non-existent column being tolerated by Postgres for SELECT * style
+-- queries — but `prisma.medicationSchedule.create({ data: { daysOfWeek }})`
+-- would fail loudly the moment a user supplied a non-default
+-- recurrence string.
+--
+-- Add the column nullable + default NULL so existing rows mean "daily"
+-- (matches the in-code semantics: `parseScheduleRecurrence(null)`
+-- returns the all-7-days set).
+ALTER TABLE "medication_schedules"
+ADD COLUMN IF NOT EXISTS "days_of_week" TEXT;