feat(loyalty): Phase 2A — transactional email notifications

Add async email notifications for 5 loyalty lifecycle events, using
the existing messaging module infrastructure (EmailService, EmailLog,
store template overrides).

- New seed script: scripts/seed/seed_email_templates_loyalty.py
  Seeds 5 templates × 4 locales (en/fr/de/lb) = 20 rows. Idempotent.
  Renamed existing script to seed_email_templates_core.py.
- Celery task: loyalty.send_notification_email — async dispatch with
  3 retries and 60s backoff. Opens own DB session.
- Notification service: LoyaltyNotificationService with 5 methods
  that resolve customer/card/program into template variables and
  enqueue via Celery (never blocks request handlers).
- Enrollment: sends loyalty_enrollment + loyalty_welcome_bonus (if
  bonus > 0) after card creation commit.
- Stamps: sends loyalty_reward_ready when stamp target reached.
- Expiration task: sends loyalty_points_expiring 14 days before expiry
  (tracked via new last_expiration_warning_at column to prevent dupes),
  and loyalty_points_expired after points are zeroed.
- Migration loyalty_005: adds last_expiration_warning_at to cards.
- 8 new unit tests for notification service dispatch.
- Fix: rate limiter autouse fixture in integration tests to prevent
  state bleed between tests.

Templates: loyalty_enrollment, loyalty_welcome_bonus,
loyalty_points_expiring, loyalty_points_expired, loyalty_reward_ready.
All support store-level overrides via the existing email template UI.

Birthday + re-engagement emails deferred to future marketing module
(cross-platform: OMS, loyalty, hosting).

342 tests pass.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

app/modules/loyalty/tests/unit/test_notification_service.py

@@ -0,0 +1,192 @@
+"""Unit tests for LoyaltyNotificationService."""
+
+from unittest.mock import MagicMock, patch
+
+import pytest
+
+from app.modules.loyalty.services.notification_service import (
+    LoyaltyNotificationService,
+)
+
+
+@pytest.fixture
+def notification_service():
+    return LoyaltyNotificationService()
+
+
+def _make_card_stub(
+    card_id=1,
+    customer_id=10,
+    merchant_id=100,
+    enrolled_at_store_id=200,
+    card_number="1234-5678-9012",
+):
+    """Lightweight card stub for notification tests."""
+    card = MagicMock()
+    card.id = card_id
+    card.customer_id = customer_id
+    card.merchant_id = merchant_id
+    card.enrolled_at_store_id = enrolled_at_store_id
+    card.card_number = card_number
+    card.program = MagicMock()
+    card.program.display_name = "Test Rewards"
+    return card
+
+
+def _make_customer_stub(email="test@example.com", full_name="Test User"):
+    customer = MagicMock()
+    customer.id = 10
+    customer.email = email
+    customer.full_name = full_name
+    return customer
+
+
+def _make_store_stub(name="Test Store"):
+    store = MagicMock()
+    store.id = 200
+    store.name = name
+    return store
+
+
+@pytest.mark.unit
+@pytest.mark.loyalty
+class TestNotificationServiceDispatch:
+    """Verify that each notification method enqueues the correct template."""
+
+    @patch("app.modules.loyalty.tasks.notifications.send_notification_email")
+    @patch("app.modules.tenancy.services.store_service.store_service")
+    @patch("app.modules.customers.services.customer_service.customer_service")
+    def test_send_enrollment_confirmation(
+        self, mock_customer_svc, mock_store_svc, mock_task, notification_service
+    ):
+        mock_customer_svc.get_customer_by_id.return_value = _make_customer_stub()
+        mock_store_svc.get_store_by_id_optional.return_value = _make_store_stub()
+        db = MagicMock()
+        card = _make_card_stub()
+
+        notification_service.send_enrollment_confirmation(db, card)
+
+        mock_task.delay.assert_called_once()
+        call_kwargs = mock_task.delay.call_args[1]
+        assert call_kwargs["template_code"] == "loyalty_enrollment"
+        assert call_kwargs["to_email"] == "test@example.com"
+        assert "card_number" in call_kwargs["variables"]
+
+    @patch("app.modules.loyalty.tasks.notifications.send_notification_email")
+    @patch("app.modules.tenancy.services.store_service.store_service")
+    @patch("app.modules.customers.services.customer_service.customer_service")
+    def test_send_welcome_bonus(
+        self, mock_customer_svc, mock_store_svc, mock_task, notification_service
+    ):
+        mock_customer_svc.get_customer_by_id.return_value = _make_customer_stub()
+        mock_store_svc.get_store_by_id_optional.return_value = _make_store_stub()
+        db = MagicMock()
+        card = _make_card_stub()
+
+        notification_service.send_welcome_bonus(db, card, 50)
+
+        mock_task.delay.assert_called_once()
+        call_kwargs = mock_task.delay.call_args[1]
+        assert call_kwargs["template_code"] == "loyalty_welcome_bonus"
+        assert call_kwargs["variables"]["points"] == "50"
+
+    @patch("app.modules.loyalty.tasks.notifications.send_notification_email")
+    @patch("app.modules.tenancy.services.store_service.store_service")
+    @patch("app.modules.customers.services.customer_service.customer_service")
+    def test_send_welcome_bonus_skipped_for_zero_points(
+        self, mock_customer_svc, mock_store_svc, mock_task, notification_service
+    ):
+        db = MagicMock()
+        card = _make_card_stub()
+
+        notification_service.send_welcome_bonus(db, card, 0)
+
+        mock_task.delay.assert_not_called()
+
+    @patch("app.modules.loyalty.tasks.notifications.send_notification_email")
+    @patch("app.modules.tenancy.services.store_service.store_service")
+    @patch("app.modules.customers.services.customer_service.customer_service")
+    def test_send_points_expiration_warning(
+        self, mock_customer_svc, mock_store_svc, mock_task, notification_service
+    ):
+        mock_customer_svc.get_customer_by_id.return_value = _make_customer_stub()
+        mock_store_svc.get_store_by_id_optional.return_value = _make_store_stub()
+        db = MagicMock()
+        card = _make_card_stub()
+
+        notification_service.send_points_expiration_warning(
+            db, card, expiring_points=200, days_remaining=14, expiration_date="2026-05-01"
+        )
+
+        mock_task.delay.assert_called_once()
+        call_kwargs = mock_task.delay.call_args[1]
+        assert call_kwargs["template_code"] == "loyalty_points_expiring"
+        assert call_kwargs["variables"]["points"] == "200"
+        assert call_kwargs["variables"]["days_remaining"] == "14"
+
+    @patch("app.modules.loyalty.tasks.notifications.send_notification_email")
+    @patch("app.modules.tenancy.services.store_service.store_service")
+    @patch("app.modules.customers.services.customer_service.customer_service")
+    def test_send_points_expired(
+        self, mock_customer_svc, mock_store_svc, mock_task, notification_service
+    ):
+        mock_customer_svc.get_customer_by_id.return_value = _make_customer_stub()
+        mock_store_svc.get_store_by_id_optional.return_value = _make_store_stub()
+        db = MagicMock()
+        card = _make_card_stub()
+
+        notification_service.send_points_expired(db, card, 150)
+
+        mock_task.delay.assert_called_once()
+        call_kwargs = mock_task.delay.call_args[1]
+        assert call_kwargs["template_code"] == "loyalty_points_expired"
+        assert call_kwargs["variables"]["expired_points"] == "150"
+
+    @patch("app.modules.loyalty.tasks.notifications.send_notification_email")
+    @patch("app.modules.tenancy.services.store_service.store_service")
+    @patch("app.modules.customers.services.customer_service.customer_service")
+    def test_send_reward_available(
+        self, mock_customer_svc, mock_store_svc, mock_task, notification_service
+    ):
+        mock_customer_svc.get_customer_by_id.return_value = _make_customer_stub()
+        mock_store_svc.get_store_by_id_optional.return_value = _make_store_stub()
+        db = MagicMock()
+        card = _make_card_stub()
+
+        notification_service.send_reward_available(db, card, "Free Coffee")
+
+        mock_task.delay.assert_called_once()
+        call_kwargs = mock_task.delay.call_args[1]
+        assert call_kwargs["template_code"] == "loyalty_reward_ready"
+        assert call_kwargs["variables"]["reward_name"] == "Free Coffee"
+
+    @patch("app.modules.loyalty.tasks.notifications.send_notification_email")
+    @patch("app.modules.tenancy.services.store_service.store_service")
+    @patch("app.modules.customers.services.customer_service.customer_service")
+    def test_no_email_skips_dispatch(
+        self, mock_customer_svc, mock_store_svc, mock_task, notification_service
+    ):
+        """Customer without email does not trigger a send."""
+        no_email_customer = _make_customer_stub(email=None)
+        mock_customer_svc.get_customer_by_id.return_value = no_email_customer
+        db = MagicMock()
+        card = _make_card_stub()
+
+        notification_service.send_enrollment_confirmation(db, card)
+
+        mock_task.delay.assert_not_called()
+
+    @patch("app.modules.loyalty.tasks.notifications.send_notification_email")
+    @patch("app.modules.tenancy.services.store_service.store_service")
+    @patch("app.modules.customers.services.customer_service.customer_service")
+    def test_customer_not_found_skips_dispatch(
+        self, mock_customer_svc, mock_store_svc, mock_task, notification_service
+    ):
+        """Missing customer does not trigger a send."""
+        mock_customer_svc.get_customer_by_id.return_value = None
+        db = MagicMock()
+        card = _make_card_stub()
+
+        notification_service.send_enrollment_confirmation(db, card)
+
+        mock_task.delay.assert_not_called()