test(loyalty): add comprehensive test suite for loyalty module

Add tests for the loyalty module Phase 2 implementation:

Fixtures (tests/fixtures/loyalty_fixtures.py):
- test_loyalty_program: Points-based program with rewards
- test_loyalty_program_no_expiration: Program without point expiry
- test_loyalty_card: Active customer card
- test_loyalty_card_inactive: Card for expiration testing
- test_loyalty_transaction: Sample transaction
- test_staff_pin: Staff PIN for verification tests

Unit Tests (tests/unit/services/test_loyalty_services.py):
- ProgramService: Company queries, listing, filtering
- CardService: Lookup, enrollment, balance operations
- PointsService: Earn, redeem, void, adjust operations
- PinService: Creation, verification, lockout

Integration Tests (tests/integration/api/v1/loyalty/):
- Vendor API: Program settings, card management, PIN operations
- Storefront API: Endpoint existence verification

Task Tests (tests/integration/tasks/test_loyalty_tasks.py):
- Point expiration for inactive cards
- Transaction record creation on expiration
- No expiration for active cards or zero balances
- Voided total tracking

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

tests/conftest.py

@@ -167,4 +167,5 @@ pytest_plugins = [
     "tests.fixtures.message_fixtures",
     "tests.fixtures.testing_fixtures",
     "tests.fixtures.content_page_fixtures",
+    "tests.fixtures.loyalty_fixtures",
 ]