feat: integrate PYMS payment gateway, add blog/sitepage/image services, local file manager

Payment Gateway:
- Add PYMSPaymentService: IPaymentGatewayService via gRPC to PYMS microservice
- Add ZarinPalPaymentService: direct ZarinPal integration (backup)
- Register 'pyms' payment provider in DI ConfigureServices
- Add PYMS proto files (pyms_transaction.proto, pyms_public_messages.proto)
- Fix VerifyDiscountWalletCharge: pass 'OK' as status instead of Authority
- Update appsettings: PaymentProvider=pyms, sandbox mode, merchant ID

Blog System:
- Add BlogCategory, BlogPost, BlogPostImage entities and CQRS
- Add proto files and gRPC services for blog management
- Add Mapster profiles for blog responses

Content Management:
- Add SitePage entity and CQRS for static pages
- Add proto and gRPC service for site pages

Image/File Management:
- Add LocalFileManager with disk storage + base64 serving + FMS fallback
- Add ImagePathResolverInterceptor for gRPC responses
- Add ImageResolverService for explicit image resolution
- Add UploadsController for public file serving with FMS fallback
- Add PaymentCallbackController for discount order payment callbacks

Database:
- Add blog and content entity migrations
- Remove ImagePath MaxLength constraints
- Remove old FileManagementService (replaced by LocalFileManager)

src/CMSMicroservice.Application/DiscountShopCQ/Queries/GetOrderById/GetOrderByIdQuery.cs

@@ -43,4 +43,6 @@ public class OrderItemDto
     public int DiscountPercentUsed { get; set; }
     public long DiscountAmount { get; set; }
     public long FinalPrice { get; set; }
+    public string ImagePath { get; set; }
+    public string ThumbnailPath { get; set; }
 }

src/CMSMicroservice.Application/DiscountShopCQ/Queries/GetOrderById/GetOrderByIdQueryHandler.cs

@@ -53,7 +53,9 @@ public class GetOrderByIdQueryHandler : IRequestHandler<GetOrderByIdQuery, Order
                 UnitPrice = od.UnitPrice,
                 DiscountPercentUsed = od.DiscountPercentUsed,
                 DiscountAmount = od.DiscountAmount,
-                FinalPrice = od.FinalPrice
+                FinalPrice = od.FinalPrice,
+                ImagePath = od.Product.ImagePath ?? "",
+                ThumbnailPath = od.Product.ThumbnailPath ?? ""
             }).ToList()
         };
     }