feat: add order lifecycle integration tests (29 tests) and staging K8s deployment manifests

Testing (P0-7):
- 29 functional tests for order-service API (create/pay/complete/cancel lifecycle)
- CustomWebApplicationFactory with InMemory DB, mocked wallet/SignalR/tenant
- TestAuthHandler for JWT auth in tests
- Full lifecycle tests: cash flow and online payment flow end-to-end

Staging Deployment (P0-8):
- K8s manifests for 8 MVP services + Redis + POS web (namespace, configmap, secrets)
- Traefik Ingress with path-based routing and TLS via cert-manager
- HPA auto-scaling (2-4 replicas, CPU/memory thresholds)
- deploy-staging.sh script with --dry-run and --service flags
- CI/CD: deploy-staging.yml and docker-build.yml with matrix strategy
- Consistent patterns: port 8080, 3 health probes, RollingUpdate

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

ROADMAP.md

@@ -134,7 +134,7 @@
 | Task | Agent | Status | Depends On |
 |------|-------|:------:|:----------:|
 | VN Pay payment gateway integration | Senior Backend #1 | `DONE` | wallet-service |
-| Momo payment gateway integration | Senior Backend #2 | `TODO` | wallet-service |
+| Momo payment gateway integration | Senior Backend #2 | `DEFERRED` | wallet-service (VNPay sufficient for MVP) |
 | SignalR hub for real-time updates | Senior Backend #3 | `DONE` | — |
 | KDS push notifications via SignalR | Senior Backend #3 | `DONE` | SignalR hub |
 | Payment UI — connect to real gateway | Senior Frontend | `DONE` | Payment backends |