Add outdated dependency check workflow

[Sahithbasani]

Summary

Adds a check-outdated GitHub Actions workflow that runs dotnet-outdated across the main library, template, and sample solutions.

The workflow reports outdated packages in the CI job summary and creates or updates tracking issues for outdated package/version combinations, including the affected solutions/projects in the issue body.

Validation

• PowerShell syntax check passed for .github/scripts/check-outdated.ps1
• Ran template-only dry run with -DryRun -Groups Template
• Confirmed dry run writes the summary and issue body files without creating or editing GitHub issues

Fixes #568