feat(dashboard): ADS-B live global aircraft overlay

Adds a live aircraft toggle to the map powered by the ADS-B Exchange
public API, proxied server-side to avoid CORS restrictions.

Features:
- Toggle button on map (bottom-right controls) — activates/deactivates
- Server-side /api/adsb proxy endpoint with 30s cache (adsb.lol)
- Renders on both 3D globe and flat map modes
- Military detection via ICAO hex prefix table + callsign patterns
  (dbFlags & 1 from adsb.lol also used where available)
- Altitude-corrected globe points (adsb.lol reports feet, not meters)
- Civil aircraft capped at 4000 to prevent map saturation; all
  military always shown regardless of total count
- Flat map: 1.8px civilian dots, 3.5px military dots, 800 civil cap
- ADS-B panel card in left rail shows live counts (airborne / mil / civ)
  and replaces the formerly empty Conflict Events row
- Auto-refreshes every 30 seconds while active
- Hides flight corridor arcs while ADS-B is active to reduce clutter
- Restores flight corridors on deactivation

API: GET /api/adsb → proxies https://api.adsb.lol/v2/lat/0/lon/0/dist/99999
No API key required. Global coverage. 30s server-side cache.

Author: Richard Fitts