Remove placeholder DbConfig registration from DI

DbConfig is no longer registered as a singleton in the dependency injection setup. This prevents accidental injection and avoids runtime NotImplementedException errors. The related comment about service lifetimes remains for future review.

EnvelopeGenerator.ServiceHost/Extensions/DependencyInjection.cs

@@ -21,8 +21,6 @@ public static class DependencyInjection
         services.AddSingleton<State>();
         services.AddScoped<MSSQLServer>();
 
-        services.AddSingleton<DbConfig>(_ => throw new NotImplementedException());
-
         //TODO: Check lifetime of services. They might be singeton.
         services.AddTransient<GdViewer>();
         // Add LicenseManager