Re-enable MVVMTK0045 analyzer

[CommunityToolkit.Mvvm](https://www.nuget.org/packages/CommunityToolkit.Mvvm) shipped analyzers with more recent versions—specifically [MVVMTK0045](https://learn.microsoft.com/en-us/dotnet/communitytoolkit/mvvm/generators/errors/mvvmtk0045).

We're not able to resolve these warnings without setting `preview`, which I don't want to do for production builds.

This issue is to track that I've disabled MVVMTK0045 in the [EditorConfig](https://github.com/bcgov/visitz-app/blob/production/visitz/.editorconfig) file and it should be re-enabled once the MVVM toolkit is updated to use C# 14.

Start in visitz/.editorconfig, where MVVMTK0045 is disabled, and check the current CommunityToolkit.Mvvm version and C# language configuration. Re-enable the analyzer only after the MVVM toolkit supports C# 14 without requiring LangVersion preview, then verify that production builds no longer need the preview setting and the warnings are resolvable.

Written by the indexing model from the issue text.