Refactor HTTP client name constant usage

Replaced the old HttpClientName constant in Constants.cs with a new Http.ClientName in the ReC.Application.Common.Constants namespace. Updated all references and using directives accordingly to improve code organization and maintainability.

src/ReC.Application/DependencyInjection.cs

@@ -2,8 +2,8 @@
 using MediatR;
 using Microsoft.Extensions.Configuration;
 using Microsoft.Extensions.DependencyInjection;
-using ReC.Application.Common;
 using ReC.Application.Common.Behaviors;
+using ReC.Application.Common.Constants;
 using ReC.Application.Common.Options;
 using System.Reflection;
 
@@ -36,7 +36,7 @@ public static class DependencyInjection
             cfg.LicenseKey = configOpt.LuckyPennySoftwareLicenseKey;
         });
 
-        services.AddHttpClient(Constants.HttpClientName)
+        services.AddHttpClient(Http.ClientName)
             .ConfigurePrimaryHttpMessageHandler(() => new HttpClientHandler
             {
                 UseDefaultCredentials = false