Update NuGet packages for restore vulnerability gate

[KSemenenko]

Summary

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

Failure

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.

Acceptance criteria

• Central package versions are updated to safe/current available NuGet versions.
• dotnet restore ./PrompterOne.slnx succeeds under warning-as-error policy.
• dotnet build ./PrompterOne.slnx -warnaserror succeeds.
• Relevant tests pass before review.
• Commit references this issue and is pushed to main for review.

[KSemenenko]

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.