Add SSH gateway operations

[wk1995]

Summary

• add a password-authenticated, operations-only SSH setup for Ubuntu gateways
• provide neurobridge-ops status, historical logs, live logs, audit records, deployments, and service controls
• bind SSH to the configured private address and allowed source range; root login, public-key login, forwarding, tunnels, and X11 are disabled
• clear or reject every residual sshd listener before starting the hardened service, including an old listener on port 22 when a custom port is configured
• document the operations workflow and record the deployment change

Validation

• python3 -m unittest -v tests.test_deployment
• bash -n linux/configure-ssh-operations.sh linux/setup-ssh-operations.sh
• python3 tools/check-version-registry.py