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/BlogCategoryCQ/Commands/CreateBlogCategory/CreateBlogCategoryCommand.cs

@@ -0,0 +1,13 @@
+using MediatR;
+
+namespace CMSMicroservice.Application.BlogCategoryCQ.Commands.CreateBlogCategory;
+
+public class CreateBlogCategoryCommand : IRequest<long>
+{
+    public string Title { get; set; } = default!;
+    public string Slug { get; set; } = default!;
+    public string? Description { get; set; }
+    public string? IconName { get; set; }
+    public int SortOrder { get; set; }
+    public bool IsActive { get; set; } = true;
+}

src/CMSMicroservice.Application/BlogCategoryCQ/Commands/CreateBlogCategory/CreateBlogCategoryCommandHandler.cs

@@ -0,0 +1,33 @@
+using CMSMicroservice.Application.Common.Interfaces;
+using CMSMicroservice.Domain.Entities.Blog;
+using MediatR;
+
+namespace CMSMicroservice.Application.BlogCategoryCQ.Commands.CreateBlogCategory;
+
+public class CreateBlogCategoryCommandHandler : IRequestHandler<CreateBlogCategoryCommand, long>
+{
+    private readonly IApplicationDbContext _context;
+
+    public CreateBlogCategoryCommandHandler(IApplicationDbContext context)
+    {
+        _context = context;
+    }
+
+    public async Task<long> Handle(CreateBlogCategoryCommand request, CancellationToken cancellationToken)
+    {
+        var entity = new BlogCategory
+        {
+            Title = request.Title,
+            Slug = request.Slug.ToLower(),
+            Description = request.Description,
+            IconName = request.IconName,
+            SortOrder = request.SortOrder,
+            IsActive = request.IsActive
+        };
+
+        _context.BlogCategories.Add(entity);
+        await _context.SaveChangesAsync(cancellationToken);
+
+        return entity.Id;
+    }
+}

src/CMSMicroservice.Application/BlogCategoryCQ/Commands/CreateBlogCategory/CreateBlogCategoryCommandValidator.cs

@@ -0,0 +1,24 @@
+using FluentValidation;
+
+namespace CMSMicroservice.Application.BlogCategoryCQ.Commands.CreateBlogCategory;
+
+public class CreateBlogCategoryCommandValidator : AbstractValidator<CreateBlogCategoryCommand>
+{
+    public CreateBlogCategoryCommandValidator()
+    {
+        RuleFor(x => x.Title)
+            .NotEmpty().WithMessage("عنوان دسته‌بندی الزامی است")
+            .MaximumLength(200).WithMessage("عنوان دسته‌بندی حداکثر ۲۰۰ کاراکتر");
+
+        RuleFor(x => x.Slug)
+            .NotEmpty().WithMessage("اسلاگ الزامی است")
+            .MaximumLength(200).WithMessage("اسلاگ حداکثر ۲۰۰ کاراکتر")
+            .Matches(@"^[a-z0-9\-]+$").WithMessage("اسلاگ فقط شامل حروف کوچک، اعداد و خط تیره");
+
+        RuleFor(x => x.Description)
+            .MaximumLength(1000).WithMessage("توضیحات حداکثر ۱۰۰۰ کاراکتر");
+
+        RuleFor(x => x.IconName)
+            .MaximumLength(100).WithMessage("نام آیکون حداکثر ۱۰۰ کاراکتر");
+    }
+}

src/CMSMicroservice.Application/BlogCategoryCQ/Commands/DeleteBlogCategory/DeleteBlogCategoryCommand.cs

@@ -0,0 +1,8 @@
+using MediatR;
+
+namespace CMSMicroservice.Application.BlogCategoryCQ.Commands.DeleteBlogCategory;
+
+public class DeleteBlogCategoryCommand : IRequest<Unit>
+{
+    public long Id { get; set; }
+}

src/CMSMicroservice.Application/BlogCategoryCQ/Commands/DeleteBlogCategory/DeleteBlogCategoryCommandHandler.cs

@@ -0,0 +1,29 @@
+using CMSMicroservice.Application.Common.Exceptions;
+using CMSMicroservice.Application.Common.Interfaces;
+using CMSMicroservice.Domain.Entities.Blog;
+using MediatR;
+
+namespace CMSMicroservice.Application.BlogCategoryCQ.Commands.DeleteBlogCategory;
+
+public class DeleteBlogCategoryCommandHandler : IRequestHandler<DeleteBlogCategoryCommand, Unit>
+{
+    private readonly IApplicationDbContext _context;
+
+    public DeleteBlogCategoryCommandHandler(IApplicationDbContext context)
+    {
+        _context = context;
+    }
+
+    public async Task<Unit> Handle(DeleteBlogCategoryCommand request, CancellationToken cancellationToken)
+    {
+        var entity = await _context.BlogCategories.FindAsync(new object[] { request.Id }, cancellationToken);
+        if (entity == null || entity.IsDeleted)
+            throw new NotFoundException(nameof(BlogCategory), request.Id);
+
+        entity.IsDeleted = true;
+
+        await _context.SaveChangesAsync(cancellationToken);
+
+        return Unit.Value;
+    }
+}

src/CMSMicroservice.Application/BlogCategoryCQ/Commands/UpdateBlogCategory/UpdateBlogCategoryCommand.cs

@@ -0,0 +1,14 @@
+using MediatR;
+
+namespace CMSMicroservice.Application.BlogCategoryCQ.Commands.UpdateBlogCategory;
+
+public class UpdateBlogCategoryCommand : IRequest<Unit>
+{
+    public long Id { get; set; }
+    public string Title { get; set; } = default!;
+    public string Slug { get; set; } = default!;
+    public string? Description { get; set; }
+    public string? IconName { get; set; }
+    public int SortOrder { get; set; }
+    public bool IsActive { get; set; }
+}

src/CMSMicroservice.Application/BlogCategoryCQ/Commands/UpdateBlogCategory/UpdateBlogCategoryCommandHandler.cs

@@ -0,0 +1,34 @@
+using CMSMicroservice.Application.Common.Exceptions;
+using CMSMicroservice.Application.Common.Interfaces;
+using CMSMicroservice.Domain.Entities.Blog;
+using MediatR;
+
+namespace CMSMicroservice.Application.BlogCategoryCQ.Commands.UpdateBlogCategory;
+
+public class UpdateBlogCategoryCommandHandler : IRequestHandler<UpdateBlogCategoryCommand, Unit>
+{
+    private readonly IApplicationDbContext _context;
+
+    public UpdateBlogCategoryCommandHandler(IApplicationDbContext context)
+    {
+        _context = context;
+    }
+
+    public async Task<Unit> Handle(UpdateBlogCategoryCommand request, CancellationToken cancellationToken)
+    {
+        var entity = await _context.BlogCategories.FindAsync(new object[] { request.Id }, cancellationToken);
+        if (entity == null || entity.IsDeleted)
+            throw new NotFoundException(nameof(BlogCategory), request.Id);
+
+        entity.Title = request.Title;
+        entity.Slug = request.Slug.ToLower();
+        entity.Description = request.Description;
+        entity.IconName = request.IconName;
+        entity.SortOrder = request.SortOrder;
+        entity.IsActive = request.IsActive;
+
+        await _context.SaveChangesAsync(cancellationToken);
+
+        return Unit.Value;
+    }
+}

src/CMSMicroservice.Application/BlogCategoryCQ/Commands/UpdateBlogCategory/UpdateBlogCategoryCommandValidator.cs

@@ -0,0 +1,27 @@
+using FluentValidation;
+
+namespace CMSMicroservice.Application.BlogCategoryCQ.Commands.UpdateBlogCategory;
+
+public class UpdateBlogCategoryCommandValidator : AbstractValidator<UpdateBlogCategoryCommand>
+{
+    public UpdateBlogCategoryCommandValidator()
+    {
+        RuleFor(x => x.Id)
+            .GreaterThan(0).WithMessage("شناسه دسته‌بندی نامعتبر است");
+
+        RuleFor(x => x.Title)
+            .NotEmpty().WithMessage("عنوان دسته‌بندی الزامی است")
+            .MaximumLength(200).WithMessage("عنوان دسته‌بندی حداکثر ۲۰۰ کاراکتر");
+
+        RuleFor(x => x.Slug)
+            .NotEmpty().WithMessage("اسلاگ الزامی است")
+            .MaximumLength(200).WithMessage("اسلاگ حداکثر ۲۰۰ کاراکتر")
+            .Matches(@"^[a-z0-9\-]+$").WithMessage("اسلاگ فقط شامل حروف کوچک، اعداد و خط تیره");
+
+        RuleFor(x => x.Description)
+            .MaximumLength(1000).WithMessage("توضیحات حداکثر ۱۰۰۰ کاراکتر");
+
+        RuleFor(x => x.IconName)
+            .MaximumLength(100).WithMessage("نام آیکون حداکثر ۱۰۰ کاراکتر");
+    }
+}