feat: Add SOC2-oriented Kubernetes baseline example

[anmolnagpal]

Summary

• Added new example: _examples/soc2-baseline/
  • main.tf
  • outputs.tf
  • versions.tf
  • README.md
• Added tf-check workflow job for new example path

What this baseline demonstrates

• HA control plane enabled
• Controlled upgrade posture (manual wave-ready)
• Defined maintenance window
• Critical vs application node-pool separation
• Audit/evidence-friendly tagging conventions

Notes

• This is a technical baseline and does not claim certification by itself.
• README includes explicit manual controls still required for SOC2 readiness.

[anmolnagpal]

Reviewed CI results: failing jobs are in soc2-baseline init/validate and one formatting bootstrap step. I could not reproduce locally in this runner because Terraform CLI is unavailable; please run terraform fmt + terraform init/validate in _examples/soc2-baseline locally and push fixes.