Add maintenance windows and weather overlay (backend)
Maintenance Windows:
- maintenance_windows table with org/site/device scoping
- Full CRUD context (Towerops.Maintenance)
- device_in_maintenance?/1 checks device → site → org hierarchy
- Alert suppression in DeviceMonitorWorker (skips alerts during maintenance)
- maintenance_badge/1 helper for UI display
Weather Overlay:
- weather_observations + weather_alerts tables
- OpenWeatherMap free API client (lat/lon based)
- WeatherSyncWorker (Oban, 15min interval, respects rate limits)
- Observation parsing from OWM response format
- Correlation helpers: severe_weather_near?/2, weather_at/2
- Severity classification tuned for WISP ops (wind, rain, ice thresholds)
- Per-org latest observations query for dashboard
- 30-day automatic cleanup
Both features are backend-only — no UI yet.
Graham McIntie
5b786aac08