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.Infrastructure/Persistence/Configurations/Blog/BlogPostCategoryConfiguration.cs

@@ -0,0 +1,22 @@
+using CMSMicroservice.Domain.Entities.Blog;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Metadata.Builders;
+
+namespace CMSMicroservice.Infrastructure.Persistence.Configurations.Blog;
+
+public class BlogPostCategoryConfiguration : IEntityTypeConfiguration<BlogPostCategory>
+{
+    public void Configure(EntityTypeBuilder<BlogPostCategory> builder)
+    {
+        builder.ToTable("BlogPostCategories");
+        builder.HasKey(e => e.Id);
+
+        builder.HasOne(d => d.BlogPost)
+            .WithMany(p => p.BlogPostCategories)
+            .HasForeignKey(d => d.BlogPostId);
+
+        builder.HasOne(d => d.BlogCategory)
+            .WithMany(p => p.BlogPostCategories)
+            .HasForeignKey(d => d.BlogCategoryId);
+    }
+}