fix(transport): carry Transport + OAuth2 authority/scope on SmtpConfigDto (OAuth2 fields were silently dropped)

tests/ZB.MOM.WW.ScadaBridge.Transport.IntegrationTests/RoundTripEquivalenceTests.cs

@@ -633,6 +633,12 @@ public sealed class RoundTripEquivalenceTests : IDisposable
                 MaxConcurrentConnections = 4,
                 MaxRetries = 9,
                 RetryDelay = TimeSpan.FromSeconds(33),
+                // Non-sensitive delivery metadata. Left null, these three were
+                // silently dropped by the bundle without the guard noticing
+                // (null == null), so they are seeded explicitly here.
+                Transport = "Ews",
+                OAuth2Authority = "https://login.example.test/token",
+                OAuth2Scope = "https://mail.example.test/.default",
             });
             await ctx.SaveChangesAsync();
         });