[SCR-5] Merge upstream PR #830: Add Prometheus metrics support

[Starosdev]

Summary

Merge the Prometheus metrics support PR from upstream (AnalogJ#830).

Why

Prometheus integration enables:

• Integration with existing monitoring stacks (Grafana, AlertManager)
• Custom alerting rules beyond built-in notifications
• Historical metrics in external time-series databases
• Multi-instance aggregation

Upstream PR

AnalogJ#830

Acceptance Criteria

• PR merged cleanly into fork
• Prometheus endpoint /metrics exposed
• Documentation updated
• Docker images include metrics support

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Linear: SCR-5
Sprint: Sprint 2: Merge Upstream PRs