backup-tool/docs/release/m18-operator-guide-evidence.md

M18 operator guide evidence

• Added docs/runbooks/operator-console.md, a task-oriented guide for first setup, repositories, sources, jobs, executions, backups/restores, notifications, and administration.
• Linked the guide from the documentation index without removing the existing operator-UI-plan entry.
• Documents write-only-secret handling and CLI-only recovery/deletion boundaries.

Verification: make check passed (107 unit/contract, 73 integration with one skipped, 15 fault, and 33 security tests; lint, typecheck, and frontend build passed).