Update NuGet packages for restore vulnerability gate

Summary

Update NuGet packages to current safe versions so CI restore no longer fails with NU1902 for transitive OpenTelemetry.Api 1.13.1.

GitHub Actions restore fails because warnings are treated as errors:

OpenTelemetry.Api 1.13.1 has GHSA-g94r-2vxg-569j moderate vulnerability.
Restore fails across Core, Shared, Web, and test projects through transitive dependency resolution.

@byskyphy

Pushed to main for review.

Commit: 8e97fa5 Update NuGet packages for restore gate (#48)

What changed:

Updated central package versions to current stable NuGet versions for the repo's .NET 10 dependency line.
Added central transitive pinning and pinned OpenTelemetry.Api to 1.15.3 so restore no longer resolves vulnerable 1.13.1.

Verification passed locally:

dotnet restore ./PrompterOne.slnx
dotnet package list --project ./PrompterOne.slnx --vulnerable --include-transitive
dotnet build ./PrompterOne.slnx -warnaserror --no-restore
dotnet test @./tests/dotnet-test-progress.rsp --solution ./PrompterOne.slnx

Full solution result: 1127/1127 passed. Assigned to @byskyphy for review.