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/BlogCategoryService.cs

@@ -0,0 +1,116 @@
+using CMSMicroservice.Protobuf.Protos.BlogCategory;
+using CMSMicroservice.WebApi.Common.Services;
+using CMSMicroservice.Application.BlogCategoryCQ.Commands.CreateBlogCategory;
+using CMSMicroservice.Application.BlogCategoryCQ.Commands.UpdateBlogCategory;
+using CMSMicroservice.Application.BlogCategoryCQ.Commands.DeleteBlogCategory;
+using CMSMicroservice.Application.BlogCategoryCQ.Queries.GetBlogCategory;
+using CMSMicroservice.Application.BlogCategoryCQ.Queries.GetAllBlogCategories;
+using CMSMicroservice.Application.BlogCategoryCQ.Queries.GetActiveBlogCategories;
+using Google.Protobuf.WellKnownTypes;
+using Grpc.Core;
+using Mapster;
+using MediatR;
+using AppModels = CMSMicroservice.Application.Common.Models;
+using ProtoMetaData = CMSMicroservice.Protobuf.Protos.MetaData;
+
+namespace CMSMicroservice.WebApi.Services;
+
+public class BlogCategoryService : BlogCategoryContract.BlogCategoryContractBase
+{
+    private readonly ISender _sender;
+    private readonly IDispatchRequestToCQRS _dispatchRequestToCQRS;
+
+    public BlogCategoryService(ISender sender, IDispatchRequestToCQRS dispatchRequestToCQRS)
+    {
+        _sender = sender;
+        _dispatchRequestToCQRS = dispatchRequestToCQRS;
+    }
+
+    public override async Task<CreateBlogCategoryResponse> CreateBlogCategory(CreateBlogCategoryRequest request, ServerCallContext context)
+    {
+        return await _dispatchRequestToCQRS.Handle<CreateBlogCategoryRequest, CreateBlogCategoryCommand, CreateBlogCategoryResponse>(request, context);
+    }
+
+    public override async Task<Empty> UpdateBlogCategory(UpdateBlogCategoryRequest request, ServerCallContext context)
+    {
+        return await _dispatchRequestToCQRS.Handle<UpdateBlogCategoryRequest, UpdateBlogCategoryCommand>(request, context);
+    }
+
+    public override async Task<Empty> DeleteBlogCategory(DeleteBlogCategoryRequest request, ServerCallContext context)
+    {
+        return await _dispatchRequestToCQRS.Handle<DeleteBlogCategoryRequest, DeleteBlogCategoryCommand>(request, context);
+    }
+
+    public override async Task<GetBlogCategoryResponse> GetBlogCategory(GetBlogCategoryRequest request, ServerCallContext context)
+    {
+        var query = new GetBlogCategoryQuery { Id = request.Id };
+        var result = await _sender.Send(query, context.CancellationToken);
+        return MapCategoryToResponse(result);
+    }
+
+    public override async Task<GetAllBlogCategoriesResponse> GetAllBlogCategories(GetAllBlogCategoriesRequest request, ServerCallContext context)
+    {
+        var query = new GetAllBlogCategoriesQuery
+        {
+            PageNumber = request.PaginationState?.PageNumber ?? 1,
+            PageSize = request.PaginationState?.PageSize ?? 20,
+            SearchTerm = request.SortBy
+        };
+
+        var result = await _sender.Send(query, context.CancellationToken);
+        var response = new GetAllBlogCategoriesResponse
+        {
+            MetaData = result.MetaData.Adapt<ProtoMetaData>()
+        };
+
+        foreach (var item in result.Models)
+            response.Models.Add(MapToListItem(item));
+
+        return response;
+    }
+
+    public override async Task<GetActiveBlogCategoriesResponse> GetActiveBlogCategories(GetActiveBlogCategoriesRequest request, ServerCallContext context)
+    {
+        var query = new GetActiveBlogCategoriesQuery();
+        var result = await _sender.Send(query, context.CancellationToken);
+
+        var response = new GetActiveBlogCategoriesResponse();
+        foreach (var item in result)
+            response.Categories.Add(MapToListItem(item));
+
+        return response;
+    }
+
+    // ── Private Mapping Helpers ──
+
+    private static GetBlogCategoryResponse MapCategoryToResponse(BlogCategoryDto dto)
+    {
+        return new GetBlogCategoryResponse
+        {
+            Id = dto.Id,
+            Title = dto.Title ?? string.Empty,
+            Slug = dto.Slug ?? string.Empty,
+            Description = dto.Description,
+            IconName = dto.IconName,
+            SortOrder = dto.SortOrder,
+            IsActive = dto.IsActive,
+            PostCount = dto.PostCount,
+            Created = dto.Created != default ? Timestamp.FromDateTime(DateTime.SpecifyKind(dto.Created, DateTimeKind.Utc)) : null
+        };
+    }
+
+    private static BlogCategoryListItem MapToListItem(BlogCategoryDto dto)
+    {
+        return new BlogCategoryListItem
+        {
+            Id = dto.Id,
+            Title = dto.Title ?? string.Empty,
+            Slug = dto.Slug ?? string.Empty,
+            Description = dto.Description,
+            IconName = dto.IconName,
+            SortOrder = dto.SortOrder,
+            IsActive = dto.IsActive,
+            PostCount = dto.PostCount
+        };
+    }
+}