Add configurable CPU temperature source

[FerdinandSu]

Summary

• Add a configurable CPU temperature source in Hardware & Sensors settings.
• List CPU temperature sensor entries so AMD users can choose entries such as Tctl/Tdie or CCD temperatures.
• Persist the selected CPU temperature sensor and prefer it when reading CPU.Temp.
• Make the optional readme content copy conditional so local builds do not fail when the file is absent.

Validation

• Built with dotnet build LiteMonitor.csproj -nologo -c Debug /clp:ErrorsOnly.