[656] Uplift to dotnet 9

[philosowaffle]

#656, #672

[philosowaffle]

Publishing locally, the windows app runs fine. However the version published from the GHA fails to launch with error:

Activation context generation failed for "C:\Users\Bailey\Downloads\ui_win-x64_330-12584185374\publish\ClientUI.exe". Dll redirector contributor unable to add file map entry for file Microsoft.ui.xaml.dll; Two or more components referenced directly or indirectly by the application manifest have files by the same name.

This seems like the closest relevant fix, however SDK version 1.7 has not been released yet.

I think I will merge this so I can unblock other work, but will log a bug against v5 to revisit why the Windows App build is broken, that will be a blocker to releasing v5.