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/Common/Interfaces/IPaymentGatewayService.cs

@@ -27,6 +27,24 @@ public interface IPaymentGatewayService
         string verificationToken, 
         CancellationToken cancellationToken = default);
     
+    /// <summary>
+    /// تأیید پرداخت با مبلغ — برای درگاه‌هایی مثل زرین‌پال که مبلغ را در Verify نیاز دارند
+    /// </summary>
+    /// <param name="refId">شماره مرجع تراکنش (Authority در زرین‌پال)</param>
+    /// <param name="verificationToken">توکن تأیید از درگاه (Status در زرین‌پال)</param>
+    /// <param name="amountInToman">مبلغ تراکنش به تومان</param>
+    /// <param name="cancellationToken"></param>
+    /// <returns>وضعیت نهایی تراکنش</returns>
+    Task<PaymentVerificationResult> VerifyPaymentAsync(
+        string refId, 
+        string verificationToken,
+        decimal amountInToman,
+        CancellationToken cancellationToken = default)
+    {
+        // پیش‌فرض: درگاه‌هایی که Amount نمی‌خواهند، از overload بدون amount استفاده کنند
+        return VerifyPaymentAsync(refId, verificationToken, cancellationToken);
+    }
+    
     /// <summary>
     /// واریز مبلغ به حساب کاربر (برداشت از کیف پول)
     /// </summary>