feat(build): add NuGet Central Package Management and upgrade dependencies

[ncipollina]

🚀 Pull Request

📋 Summary

• Introduce Directory.Packages.props to centralize all NuGet package version management across the solution
• Remove Version attributes from all PackageReference entries in .csproj files and Directory.Build.props
• Consolidate TFM-conditional ItemGroups in project files — versions are now managed centrally via TFM-pinned groups in Directory.Packages.props
• Upgrade all packages to latest versions (AWS SDK, Microsoft.Extensions, OpenTelemetry, testing packages, SourceLink)
• Add Directory.Packages.props to Solution Items in the .slnx file
• Bump VersionPrefix to 1.2.4

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✅ Checklist

• My changes build cleanly
• I've added/updated relevant tests
• I've added/updated documentation or README
• I've followed the coding style for this project
• I've tested the changes locally (if applicable)

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🧪 Related Issues or PRs

N/A

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💬 Notes for Reviewers

The Directory.Packages.props is organized with labeled ItemGroups (AWS SDK, Microsoft, Microsoft TFM pinned, OpenTelemetry, Testing) following the same pattern used in other LayeredCraft repos. TFM-conditional package versions for Microsoft.Extensions.* are pinned per target framework (net8.0, net9.0, net10.0) in the central file, which allowed removing the conditional ItemGroups from individual .csproj files.

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