📡 Relocate scheduled monitoring off the public repo

[sepehrsadri]

The scheduled monitoring workflows (health-check.yml, ripe-atlas-check.yml) had their schedule: triggers removed before going public, because on a public repo the run logs would expose live endpoints / measurement targets, and public cron auto-disables after 60 days of inactivity anyway. They are currently manual-dispatch only.

Track the proper long-term home for monitoring:

• Move active monitoring to a private repo or an external scheduler
• Strip/mask real hostnames, IPs, and .target values from any logged output
• If any scheduled run stays here, add a keep-alive so it isn't silently disabled after 60 days

Until then, run them by hand with workflow_dispatch.