feat(ADM-018): completed feature

work/artifacts/F-024/architect.md

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+# Architect — F-024 Notifications: transactional email
+
+## Feature
+F-024 sends transactional emails driven by domain events with idempotency per event id and a swappable provider.
+
+## Design
+
+### Module boundaries
+Create `project/src/modules/notifications/` with domain/application/infrastructure/api/tests. Notifications owns message persistence and provider dispatch; domain code uses only the `EmailProvider` interface.
+
+### Data model
+Add migration `018_notifications.js`:
+- `notifications_messages`: id, event_id text unique, channel text default 'email', template text, recipient text, subject text, body text, status text default 'sent', created_at timestamptz.
+- UNIQUE `event_id` for idempotency.
+
+### Templates
+- `order_confirmation`, `payment_failed`, `order_shipped` mapped to events `OrderPaid`, `PaymentFailed`, `OrderShipped`.
+
+### API
+- Internal `/notifications/dispatch` (admin/test) to trigger a dispatch by template and recipient.
+- Internal `/notifications/messages/:eventId` to inspect dispatch status.
+
+## Acceptance trace
+- PaymentSucceeded -> order_confirmation email queued, idempotent on event_id.
+- Replay same event -> no duplicate row.
+- Provider swap touches only infrastructure.