Add Uptime Kuma for external uptime monitoring and outage alerts

[koinsaari]

Summary

Deploy Uptime Kuma on the edge VPS to monitor public Stoganet endpoints from outside the home box and send push notifications on outage.

Context

Currently there is no external monitoring — outages are only noticed when a user reports them. The edge VPS is already running and is a natural fit: it sits outside the home box, has a public IP, and monitors from the user's perspective. Uptime Kuma can push alerts via ntfy, which is already used in the backup pipeline.

Scope

• Deploy Uptime Kuma as a Docker container on the edge VPS
• Expose via Caddy subdomain (e.g. uptime.stoganet.com), NetBird-only
• Configure monitors for at minimum:
  • https://jellyfin.stoganet.com/System/Info/Public
  • https://traefik.stoganet.com/
  • https://api.stoganet.com/ (or equivalent health endpoint)
• Alert via ntfy on status change
• Out of scope: monitoring internal services not reachable from the VPS

Acceptance criteria

• Uptime Kuma running on edge VPS, persisted across restarts
• Dashboard accessible via NetBird peers only
• All key public endpoints monitored with ≤5 min polling interval
• ntfy alert fires within one polling cycle of a simulated outage
• Config backed up or declared in code (not just UI state)

Notes

• Uptime Kuma stores state in a SQLite file — volume-mount it so restarts don't lose monitor config
• ntfy integration is built-in under Notifications
• Consider exporting monitor config as JSON and committing it so it's reproducible without the UI