fix: Change SQLExecutor service registration to scoped

Updated the `AddSQLExecutor<T>` method in the `DIExtensions` class to register `ISQLExecutor<T>` as a scoped service instead of a singleton. This ensures that a new instance of `SQLExecutor<T>` is created for each request within the same scope, improving resource management and request isolation.

EnvelopeGenerator.Infrastructure/DependencyExtensions.cs

@@ -71,7 +71,7 @@ public static class DIExtensions
 
     public static IServiceCollection AddSQLExecutor<T>(this IServiceCollection services) where T : class
     {
-        services.AddSingleton<ISQLExecutor<T>, SQLExecutor<T>>();
+        services.AddScoped<ISQLExecutor<T>, SQLExecutor<T>>();
 
         var interfaceType = typeof(ISQL<>);
         var targetGenericType = interfaceType.MakeGenericType(typeof(T));