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/Services/BlogPostImageService.cs

@@ -0,0 +1,72 @@
+using System.Linq;
+using CMSMicroservice.Protobuf.Protos.BlogPostImage;
+using CMSMicroservice.WebApi.Common.Services;
+using CMSMicroservice.Application.BlogPostImageCQ.Commands.AddBlogPostImage;
+using CMSMicroservice.Application.BlogPostImageCQ.Commands.DeleteBlogPostImage;
+using CMSMicroservice.Application.BlogPostImageCQ.Commands.ReorderBlogPostImages;
+using CMSMicroservice.Application.BlogPostImageCQ.Queries.GetBlogPostImages;
+using Google.Protobuf.WellKnownTypes;
+using Grpc.Core;
+using MediatR;
+
+namespace CMSMicroservice.WebApi.Services;
+
+public class BlogPostImageService : BlogPostImageContract.BlogPostImageContractBase
+{
+    private readonly ISender _sender;
+    private readonly IDispatchRequestToCQRS _dispatchRequestToCQRS;
+
+    public BlogPostImageService(ISender sender, IDispatchRequestToCQRS dispatchRequestToCQRS)
+    {
+        _sender = sender;
+        _dispatchRequestToCQRS = dispatchRequestToCQRS;
+    }
+
+    public override async Task<AddBlogPostImageResponse> AddBlogPostImage(AddBlogPostImageRequest request, ServerCallContext context)
+    {
+        return await _dispatchRequestToCQRS.Handle<AddBlogPostImageRequest, AddBlogPostImageCommand, AddBlogPostImageResponse>(request, context);
+    }
+
+    public override async Task<Empty> DeleteBlogPostImage(DeleteBlogPostImageRequest request, ServerCallContext context)
+    {
+        return await _dispatchRequestToCQRS.Handle<DeleteBlogPostImageRequest, DeleteBlogPostImageCommand>(request, context);
+    }
+
+    public override async Task<GetBlogPostImagesResponse> GetBlogPostImages(GetBlogPostImagesRequest request, ServerCallContext context)
+    {
+        var query = new GetBlogPostImagesQuery { BlogPostId = request.BlogPostId };
+        var result = await _sender.Send(query, context.CancellationToken);
+
+        var response = new GetBlogPostImagesResponse();
+        foreach (var item in result)
+        {
+            response.Images.Add(new BlogPostImageItem
+            {
+                Id = item.Id,
+                BlogPostId = item.BlogPostId,
+                ImagePath = item.ImagePath ?? string.Empty,
+                ThumbnailPath = item.ThumbnailPath ?? string.Empty,
+                AltText = item.AltText,
+                Caption = item.Caption,
+                SortOrder = item.SortOrder
+            });
+        }
+
+        return response;
+    }
+
+    public override async Task<Empty> ReorderBlogPostImages(ReorderBlogPostImagesRequest request, ServerCallContext context)
+    {
+        var command = new ReorderBlogPostImagesCommand
+        {
+            Items = request.Items.Select(x => new Application.BlogPostImageCQ.Commands.ReorderBlogPostImages.ImageSortItem
+            {
+                Id = x.Id,
+                SortOrder = x.SortOrder
+            }).ToList()
+        };
+
+        await _sender.Send(command, context.CancellationToken);
+        return new Empty();
+    }
+}