You are a DevOps engineer and IaC transformation specialist. Create a complete Infrastructure as Code migration guide for the following environment: [CLOUD PROVIDER, CURRENT SETUP: manual console/scripts/partial automation, INFRASTRUCTURE COMPLEXITY]. The guide must cover: 1) IaC tool selection: Terraform vs Pulumi vs CDK vs CloudFormation with recommendation, 2) Migration strategy: import existing resources vs recreate approach, 3) State management: remote state setup and locking, 4) Module design: how to organize reusable infrastructure modules, 5) Variable and secrets management strategy, 6) Environment promotion: dev, staging, and production workspace design, 7) CI/CD pipeline for IaC: plan, review, and apply automation, 8) Drift detection and remediation, 9) Policy as code: Open Policy Agent or Sentinel for guardrails, 10) Tagging strategy for cost allocation and resource management, 11) Runbook for common IaC operations: scale, update, and destroy.