Merge branch 'kub-stage' into production

Features merged:
- ZarinPal payment gateway (sandbox mode)
- Discount store improvements (100% discount auto-apply)
- VAT breakdown on checkout
- PaymentStatus in order responses (proto v0.0.179)
- ExpirePendingOrdersService (background job for stale orders)
- DeliveryStatus proper mapping + cancel on failed payment
- Inventory management system
- Various bug fixes

Production config preserved:
- DB: 45.149.79.127 / KBS
- CmsBaseUrl: https://cms.kbs1.ir
- FrontOfficeBaseUrl: https://foursat.kbs1.ir
- Payment gateway: sandbox (will show 'درگاه فعال نمیباشد')
- Production workflow unchanged

src/CMSMicroservice.WebApi/appsettings.json

@@ -1,5 +1,14 @@
 {
-  "UseRealPaymentGateway": false,
+  "PaymentProvider": "zarinpal",
+  "ZarinPal": {
+    "MerchantId": "6b098fc8-f490-47a1-aac3-1de1a1b84404",
+    "UseSandbox": true
+  },
+  "CmsBaseUrl": "https://cms.kbs1.ir",
+  "FrontOfficeBaseUrl": "https://foursat.kbs1.ir",
+  "FMS": {
+    "Address": "https://dl.afrino.co"
+  },
   "JwtSecurityKey": "TvlZVx5TJaHs8e9HgUdGzhGP2CIidoI444nAj+8+g7c=",
   "JwtIssuer": "https://localhost",
   "JwtAudience": "https://localhost",