A new project, `ReC.Domain`, has been added to the solution.
The project is included in `ReC.sln` with build configurations
for `Debug|Any CPU` and `Release|Any CPU`. It is nested under
the `src` folder in the solution structure.
The `ReC.Domain.csproj` file targets .NET 8.0, uses the
`Microsoft.NET.Sdk` SDK, and enables modern C# features such
as implicit `using` directives and nullable reference types.
