perf(medications): index the dashboard meds-today read shapes

Two additive indexes on medication_intake_events: (user_id, scheduled_for)
for the sibling reads that filter without medication_id, and
(user_id, medication_id, taken_at) for the per-medication last-taken
group-by that scanned the whole intake history on every dashboard load.
Additive migration 0253, no data change, no behaviour change.

prisma/migrations/0253_perf_medication_intake_indexes/migration.sql

@@ -0,0 +1,11 @@
+-- v1.30.12 perf — index the two medication-intake read shapes the dashboard
+-- "meds today" builder fires that could not index-seek before: the sibling
+-- reads filtering (user_id, scheduled_for) without medication_id, and the
+-- per-medication last-taken group-by that scanned the whole intake history.
+-- Additive; no data change.
+
+-- CreateIndex
+CREATE INDEX "medication_intake_events_user_id_scheduled_for_idx" ON "medication_intake_events"("user_id", "scheduled_for");
+
+-- CreateIndex
+CREATE INDEX "medication_intake_events_user_id_medication_id_taken_at_idx" ON "medication_intake_events"("user_id", "medication_id", "taken_at");

prisma/schema.prisma

@@ -2733,6 +2733,12 @@ model MedicationIntakeEvent {
   // v1.7.0 sync — keyset support for the `/api/sync/changes` intake feed
   // (`where userId` ordered by `(updatedAt asc, id asc)`).
   @@index([userId, updatedAt, id])
+  // v1.30.12 perf — the dashboard "meds today" read fires sibling queries that
+  // filter `(userId, scheduledFor)` WITHOUT `medicationId` (the composite above
+  // cannot range-seek those) and a per-medication `_max(takenAt)` group-by that
+  // scanned the whole intake history. These two let both index-seek instead.
+  @@index([userId, scheduledFor])
+  @@index([userId, medicationId, takenAt])
   @@map("medication_intake_events")
 }