[b/r] Update restore README with ci-framework and manual procedure

Update automated Quick Start to use ci-framework playbooks. Rewrite
manual restore procedure with fully rendered Restore CRs and resource
modifier ConfigMap instead of Jinja2 template references. Update Velero
version notes for OCP 4.20.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: stuggi