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/CreateBlogPost/CreateBlogPostCommandHandler.cs

@@ -0,0 +1,98 @@
+using CMSMicroservice.Application.Common.FileManager;
+using CMSMicroservice.Application.Common.Interfaces;
+using CMSMicroservice.Domain.Entities.Blog;
+using CMSMicroservice.Domain.Enums;
+using MediatR;
+using Microsoft.Extensions.Logging;
+
+namespace CMSMicroservice.Application.BlogPostCQ.Commands.CreateBlogPost;
+
+public class CreateBlogPostCommandHandler : IRequestHandler<CreateBlogPostCommand, long>
+{
+    private readonly IApplicationDbContext _context;
+    private readonly ICurrentUserService _currentUser;
+    private readonly IFileManager _fileManager;
+    private readonly ILogger<CreateBlogPostCommandHandler> _logger;
+
+    public CreateBlogPostCommandHandler(
+        IApplicationDbContext context,
+        ICurrentUserService currentUser,
+        IFileManager fileManager,
+        ILogger<CreateBlogPostCommandHandler> logger)
+    {
+        _context = context;
+        _currentUser = currentUser;
+        _fileManager = fileManager;
+        _logger = logger;
+    }
+
+    public async Task<long> Handle(CreateBlogPostCommand request, CancellationToken cancellationToken)
+    {
+        var currentUserId = _currentUser.UserId;
+        if (string.IsNullOrEmpty(currentUserId) || !long.TryParse(currentUserId, out var authorUserId))
+            throw new UnauthorizedAccessException("کاربر احراز هویت نشده است");
+
+        var post = new BlogPost
+        {
+            Title = request.Title.Trim(),
+            Slug = string.IsNullOrWhiteSpace(request.Slug)
+                ? $"post-{Guid.NewGuid():N}".Substring(0, 20)
+                : request.Slug.Trim().ToLower(),
+            Summary = request.Summary?.Trim(),
+            HtmlContent = request.HtmlContent,
+            FeaturedImagePath = request.FeaturedImagePath,
+            FeaturedImageThumbnailPath = request.FeaturedImageThumbnailPath,
+            Status = BlogPostStatus.Draft,
+            AuthorUserId = authorUserId,
+            IsFeatured = request.IsFeatured,
+            SortOrder = request.SortOrder,
+            ViewCount = 0
+        };
+
+        // آپلود تصویر شاخص (اگر فایل 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;
+        }
+
+        _context.BlogPosts.Add(post);
+        await _context.SaveChangesAsync(cancellationToken);
+
+        // افزودن دسته‌بندی‌ها
+        foreach (var categoryId in request.CategoryIds)
+        {
+            _context.BlogPostCategories.Add(new BlogPostCategory
+            {
+                BlogPostId = post.Id,
+                BlogCategoryId = categoryId
+            });
+        }
+
+        // افزودن تگ‌ها
+        foreach (var tagId in request.TagIds)
+        {
+            _context.BlogPostTags.Add(new BlogPostTag
+            {
+                BlogPostId = post.Id,
+                TagId = tagId
+            });
+        }
+
+        if (request.CategoryIds.Any() || request.TagIds.Any())
+            await _context.SaveChangesAsync(cancellationToken);
+
+        _logger.LogInformation(
+            "Blog post created. Id: {Id}, Title: {Title}, Author: {Author}",
+            post.Id, post.Title, authorUserId);
+
+        return post.Id;
+    }
+}