Clean Architecture with .NET 6

Updating our Clean Architecture template for .NET 6 involves enforcing stricter boundaries using `ImplicitUsings`.

Project References

The Core layer (`Domain`) should have ZERO dependencies. In .NET 6, we can enforce this by stripping out accidental imports.

<ItemGroup>
  <!-- Remove System.Net.Http to prevent HTTP calls in Domain -->
  <Using Remove="System.Net.Http" /> 
</ItemGroup>

This compiler-level enforcement prevents junior developers from injecting HTTP clients into Domain Entities.