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.Protobuf/Protos/products.proto

@@ -228,6 +228,7 @@ message GetAllProductsByFilterFilter
     google.protobuf.Int32Value view_count = 12;
     google.protobuf.Int32Value remaining_count = 13;
     google.protobuf.Int64Value category_id = 14;
+    google.protobuf.BoolValue is_active = 15;
 }
 message GetAllProductsByFilterResponse
 {
@@ -251,6 +252,8 @@ message GetAllProductsByFilterResponseModel
     int32 remaining_count = 13;
     // لیست شناسه دسته‌بندی‌های محصول
     repeated int64 category_ids = 14;
+    // وضعیت فعال/غیرفعال (معکوس IsDeleted)
+    bool is_active = 15;
 }
 
 message GetCustomerProductsByFilterResponse