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.WebApi/Common/Mappings/BlogCategoryProfile.cs

@@ -0,0 +1,14 @@
+using Mapster;
+using ProtoBlogCategory = CMSMicroservice.Protobuf.Protos.BlogCategory;
+
+namespace CMSMicroservice.WebApi.Common.Mappings;
+
+public class BlogCategoryProfile : IRegister
+{
+    void IRegister.Register(TypeAdapterConfig config)
+    {
+        // CreateBlogCategory: long → CreateBlogCategoryResponse
+        config.NewConfig<long, ProtoBlogCategory.CreateBlogCategoryResponse>()
+            .Map(dest => dest.Id, src => src);
+    }
+}

src/CMSMicroservice.WebApi/Common/Mappings/BlogPostProfile.cs

@@ -0,0 +1,26 @@
+using CMSMicroservice.Application.BlogPostCQ.Commands.PublishBlogPost;
+using CMSMicroservice.Application.BlogPostCQ.Commands.ArchiveBlogPost;
+using Google.Protobuf.WellKnownTypes;
+using Mapster;
+using ProtoBlogPost = CMSMicroservice.Protobuf.Protos.BlogPost;
+
+namespace CMSMicroservice.WebApi.Common.Mappings;
+
+public class BlogPostProfile : IRegister
+{
+    void IRegister.Register(TypeAdapterConfig config)
+    {
+        // PublishBlogPost: Command result → Proto response
+        config.NewConfig<PublishBlogPostResult, ProtoBlogPost.PublishBlogPostResponse>()
+            .Map(dest => dest.Success, src => src.Success)
+            .Map(dest => dest.Message, src => src.Message)
+            .Map(dest => dest.PublishedAt, src => src.PublishedAt.HasValue
+                ? Timestamp.FromDateTime(DateTime.SpecifyKind(src.PublishedAt.Value, DateTimeKind.Utc))
+                : null);
+
+        // ArchiveBlogPost: Command result → Proto response
+        config.NewConfig<ArchiveBlogPostResult, ProtoBlogPost.ArchiveBlogPostResponse>()
+            .Map(dest => dest.Success, src => src.Success)
+            .Map(dest => dest.Message, src => src.Message);
+    }
+}