feat: implement communications module with SMTP settings, email logging, and frontend UI

src/backend/Zentral.API/Apps/Communications/Dtos/TestEmailDto.cs

@@ -0,0 +1,8 @@
+namespace Zentral.API.Apps.Communications.Dtos;
+
+public class TestEmailDto
+{
+    public string To { get; set; } = string.Empty;
+    public string Subject { get; set; } = "Test Email from Zentral";
+    public string Body { get; set; } = "This is a test email sent from Zentral Communications Module.";
+}