fix(backend): make API types internal

backend/src/Socialize.Api/Infrastructure/Emailer/Services/ResendEmailSender.cs

@@ -7,7 +7,7 @@ using Microsoft.Extensions.Options;
 
 namespace Socialize.Api.Infrastructure.Emailer.Services;
 
-public class ResendEmailSender : IEmailSender
+internal class ResendEmailSender : IEmailSender
 {
     private static readonly Uri EndpointUri = new("https://api.resend.com/emails");
     private readonly HttpClient _httpClient;