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/BlogPostCQ/Commands/PublishBlogPost/PublishBlogPostCommand.cs

@@ -0,0 +1,15 @@
+using MediatR;
+
+namespace CMSMicroservice.Application.BlogPostCQ.Commands.PublishBlogPost;
+
+public class PublishBlogPostCommand : IRequest<PublishBlogPostResult>
+{
+    public long Id { get; set; }
+}
+
+public class PublishBlogPostResult
+{
+    public bool Success { get; set; }
+    public string Message { get; set; } = string.Empty;
+    public DateTime? PublishedAt { get; set; }
+}