ops: key management runbook (backup, rotation, separation)

[TheNewAutonomy]

Goal

Document and implement operational best practices for keys/identities.

Scope

• Separate keys: node identity vs wallet keys vs validator keys (if applicable)
• Backup/restore guidance
• Rotation procedure and how it impacts identity/peering
• File permissions and secret handling

Acceptance criteria

• Operator-facing runbook exists
• Tooling supports safe backups and predictable restarts