fix(infrastructure): change IImapEmailService registration from Singleton to Scoped to support scoped DbContext dependency

src/infrastructure/DigitalData.MessagingService.Infrastructure/DependencyInjection.cs

@@ -34,7 +34,7 @@ public static class DependencyInjection
 
         // Email Service - IMAP inbound (Limilabs Mail.dll)
         // Fresh connection per call — stateless and thread-safe.
-        services.AddSingleton<IImapEmailService, LimilabsImapEmailService>();
+        services.AddScoped<IImapEmailService, LimilabsImapEmailService>();
         
         // PDF Processing Service (using DevExpress.Pdf)
         services.AddScoped<IPdfProcessingService, DevExpressPdfProcessingService>();