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/UpdateBlogPost/UpdateBlogPostCommandHandler.cs

@@ -0,0 +1,88 @@
+using CMSMicroservice.Application.Common.FileManager;
+using CMSMicroservice.Application.Common.Interfaces;
+using CMSMicroservice.Domain.Entities.Blog;
+using MediatR;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.Extensions.Logging;
+
+namespace CMSMicroservice.Application.BlogPostCQ.Commands.UpdateBlogPost;
+
+public class UpdateBlogPostCommandHandler : IRequestHandler<UpdateBlogPostCommand, Unit>
+{
+    private readonly IApplicationDbContext _context;
+    private readonly IFileManager _fileManager;
+    private readonly ILogger<UpdateBlogPostCommandHandler> _logger;
+
+    public UpdateBlogPostCommandHandler(
+        IApplicationDbContext context,
+        IFileManager fileManager,
+        ILogger<UpdateBlogPostCommandHandler> logger)
+    {
+        _context = context;
+        _fileManager = fileManager;
+        _logger = logger;
+    }
+
+    public async Task<Unit> Handle(UpdateBlogPostCommand request, CancellationToken cancellationToken)
+    {
+        var post = await _context.BlogPosts.FirstOrDefaultAsync(x => x.Id == request.Id && !x.IsDeleted, cancellationToken)
+            ?? throw new KeyNotFoundException($"مقاله با شناسه {request.Id} یافت نشد");
+
+        post.Title = request.Title.Trim();
+        // حفظ slug قبلی اگر مقدار جدید خالی باشد
+        if (!string.IsNullOrWhiteSpace(request.Slug))
+            post.Slug = request.Slug.Trim().ToLower();
+        post.Summary = request.Summary?.Trim();
+        post.HtmlContent = request.HtmlContent;
+        post.FeaturedImagePath = request.FeaturedImagePath;
+        post.FeaturedImageThumbnailPath = request.FeaturedImageThumbnailPath;
+        post.IsFeatured = request.IsFeatured;
+        post.SortOrder = request.SortOrder;
+
+        // آپلود تصویر شاخص (اگر فایل جدید ارسال شده باشد)
+        if (request.ImageFileBytes is { Length: > 0 })
+        {
+            var result = await _fileManager.UploadImageAsync(
+                "Images/BlogPosts",
+                request.ImageFileBytes,
+                request.ImageFileMime ?? "image/jpeg",
+                request.ImageFileName,
+                cancellationToken);
+
+            post.FeaturedImagePath = result.Main.Path;
+            post.FeaturedImageThumbnailPath = result.Thumbnail.Path;
+        }
+
+        // بروزرسانی دسته‌بندی‌ها
+        var existingCategories = await _context.BlogPostCategories
+            .Where(x => x.BlogPostId == post.Id).ToListAsync(cancellationToken);
+        _context.BlogPostCategories.RemoveRange(existingCategories);
+        foreach (var categoryId in request.CategoryIds)
+        {
+            _context.BlogPostCategories.Add(new BlogPostCategory
+            {
+                BlogPostId = post.Id,
+                BlogCategoryId = categoryId
+            });
+        }
+
+        // بروزرسانی تگ‌ها
+        var existingTags = await _context.BlogPostTags
+            .Where(x => x.BlogPostId == post.Id).ToListAsync(cancellationToken);
+        _context.BlogPostTags.RemoveRange(existingTags);
+        foreach (var tagId in request.TagIds)
+        {
+            _context.BlogPostTags.Add(new BlogPostTag
+            {
+                BlogPostId = post.Id,
+                TagId = tagId
+            });
+        }
+
+        await _context.SaveChangesAsync(cancellationToken);
+
+        _logger.LogInformation("Blog post updated. Id: {Id}, Title: {Title}", post.Id, post.Title);
+
+        return Unit.Value;
+    }
+}