v0.2.0

Production-hardening source release.

Highlights:

• Helm chart plus AWS, GCP, and Azure deployment overlays
• explicit platformmigrate command and Helm pre-install/pre-upgrade migration job
• real readiness checks for Postgres, queue backend, OIDC discovery, GitOps path, and Kubernetes dependency
• hardened HTTP server timeouts and strict production config validation
• secret-manager-friendly config with *_FILE support and secret-backed Helm env wiring