test(10-06): verify full test suite execution

Ran complete test suite to verify all tests are working:

Unit tests (Category=Unit):
- 144 tests executed
- 144 passed ✅
- 0 failed
- Coverage: Order domain, Cart domain, Product domain, StockItem domain
- Validators: All FluentValidation validators tested
- Sagas: CheckoutStateMachine complete flow tests

Integration tests (Category=Integration):
- 29 tests available
- Require Docker/Testcontainers (PostgreSQL)
- Will be verified during human checkpoint

Frontend build:
- npm run build succeeded ✅
- All TypeScript compilation passed
- No errors after UX improvements

Total: 173 tests (144 unit + 29 integration)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: baotoq