- Add NuGet.config to override .sln-level package sources
- Telerik source was configured but not actually used (no PackageReference)
- Solution: Configure nuget.org as single source to avoid NU1507 warning-as-error
- Restores global.json allowPrerelease:false (GA SDK only, not preview)
- Enables local Release builds without SDK version conflicts
Fixes: Build failure on local machines with preview SDK 10.0.400
Verified: dotnet build KArtSell.sln -c Release → 0 errors ✅
Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>
