Add PolicyEngine infrastructure deployment patterns skill

Captures learnings from policyengine-api-v2-alpha GCP migration:
- GCP Cloud Run deployment patterns
- Terraform infrastructure as code standards
- GitHub Actions OIDC authentication setup
- Migration patterns from AWS to GCP
- Troubleshooting common deployment issues

This skill will help future Claude sessions working on PolicyEngine
infrastructure tasks by providing standardized patterns for GCP
deployment, Terraform configuration, and CI/CD setup.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: PolicyEngine-Bot