ADR-024: Azure Demo VM Deploy from GitHub Actions
Operationalises ADR-022 §3 (Phase 3f) for the dev tier: the stable demo VM at dev-azure.securityv0.com deploys on every main CI success via Azure Run Command using a new tightly-scoped Entra app + OIDC federation from GitHub Actions. No SSH key in the deploy path. Hetzner stays warm as fallback during cutover (no behavior change on the Hetzner side). PR-preview ephemeral VMs are explicitly out of scope; the design for that surface is banked in [docs/infrastructure/azure-ephemeral-pr-previews-design.md](../../infrastructure/azure-ephemeral-pr-previews-design.md) for re-activation when triggered.