Rename service registration method for clarity

Renamed the method in `DependencyInjection.cs` from `AddApplicationServices` to `AddMessagingServiceApplication` to better reflect its purpose related to the Messaging Service Application. Updated the corresponding method call in `Program.cs` to ensure consistency and correct service registration.

src/presentation/DigitalData.MessagingService.API/Program.cs

@@ -65,7 +65,7 @@ try
     builder.Configuration.AddJsonFile("appsettings.Secrets.json", optional: true, reloadOnChange: true);
 
     // Register Application layer (MediatR, AutoMapper, FluentValidation)
-    builder.Services.AddApplicationServices(builder.Configuration);
+    builder.Services.AddMessagingServiceApplication(builder.Configuration);
 
     // Register Infrastructure layer (RabbitMQ, Repositories, etc.)
     builder.Services.AddInfrastructure(builder.Configuration);