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/BlogPostImageCQ/Commands/ReorderBlogPostImages/ReorderBlogPostImagesCommand.cs

@@ -0,0 +1,14 @@
+using MediatR;
+
+namespace CMSMicroservice.Application.BlogPostImageCQ.Commands.ReorderBlogPostImages;
+
+public class ReorderBlogPostImagesCommand : IRequest<Unit>
+{
+    public List<ImageSortItem> Items { get; set; } = new();
+}
+
+public class ImageSortItem
+{
+    public long Id { get; set; }
+    public int SortOrder { get; set; }
+}

src/CMSMicroservice.Application/BlogPostImageCQ/Commands/ReorderBlogPostImages/ReorderBlogPostImagesCommandHandler.cs

@@ -0,0 +1,34 @@
+using CMSMicroservice.Application.Common.Interfaces;
+using MediatR;
+using Microsoft.EntityFrameworkCore;
+
+namespace CMSMicroservice.Application.BlogPostImageCQ.Commands.ReorderBlogPostImages;
+
+public class ReorderBlogPostImagesCommandHandler : IRequestHandler<ReorderBlogPostImagesCommand, Unit>
+{
+    private readonly IApplicationDbContext _context;
+
+    public ReorderBlogPostImagesCommandHandler(IApplicationDbContext context)
+    {
+        _context = context;
+    }
+
+    public async Task<Unit> Handle(ReorderBlogPostImagesCommand request, CancellationToken cancellationToken)
+    {
+        var ids = request.Items.Select(x => x.Id).ToList();
+        var images = await _context.BlogPostImages
+            .Where(x => ids.Contains(x.Id) && !x.IsDeleted)
+            .ToListAsync(cancellationToken);
+
+        foreach (var item in request.Items)
+        {
+            var image = images.FirstOrDefault(x => x.Id == item.Id);
+            if (image != null)
+                image.SortOrder = item.SortOrder;
+        }
+
+        await _context.SaveChangesAsync(cancellationToken);
+
+        return Unit.Value;
+    }
+}