Production cutover runbook

Superseded by `docs/runbooks/hetzner-cutover.md`.

The original v2.0 cutover (Neon / Clerk / Cloudflare → Vercel) no longer applies. Stratify is live on Hetzner (Docker + Traefik) at https://app.stratifyinvest.com behind Cloudflare Access; Vercel is deactivated. The executed cutover steps, rollback, and post-cutover dashboard updates live in docs/runbooks/hetzner-cutover.md.