Add monitoring for node health and sync status

[touchthesun]

Expose metrics and dashboards for federation health, including sync status, peer uptime, and error rates.

Acceptance Criteria

• Health metrics defined (uptime, last sync, error rate)
• Metrics exposed via API
• CLI command for federation status
• Optional dashboard output (HTML/JSON)

Dependencies

• Issue 5.4.1 (sync scheduling)

Estimated Effort

M (4-6 days)

Technical Notes

Reuse existing Prometheus hooks if available.

---

Generated from notes/github-issues.md — Issue 5.5.2