feat(fleet): draw airport ground vehicles by callsign and ground stations as a radio mast

Feeds carry many airport ground vehicles (type ZVEH) and ground stations
(GRND) that were drawn as the generic plane, some at the 10 km airborne
default.

- types.json gains aircraft_callsign rules: a ZVEH callsign starting FIRE is
  a fire truck, PUSH/TUG a pushback tug, DEICER/SQUID/SQB a van, else a car.
  GRND draws a new 11.8 m radio mast (other/radio_mast.glb).
- resolveAircraft and aircraftModelSpec take the callsign; a matched rule
  names the model outright, ahead of the type's class model.
- The layer spec cache keys such types by the rule matched, so it holds at
  most one entry per rule.
- These models (catalog category `other`) draw at their built size, as such
  models already do, and a
  contact with no altitude whose model is one now stands on the ground; the
  feed's own type is kept for such contacts, as no airframe lookup knows it.
- Local ADS-B passes the callsign too.

README.md

@@ -60,7 +60,7 @@ Start with the included data sources, then add your own. Each layer is a separat
 - **📡 Contacts:** A 250 km roster of everything near your target — step through live aircraft and drop into any cockpit.
 - **🎯 Click-to-track anything:** Camera locks on, draws a fading trail, surfaces full metadata — and a tracked fire or vessel hands you off to the nearest live camera in one click.
 - **🖊️ Voice whiteboard:** Speak annotations onto the world — real boundary polygons, marks, and routes.
-- **🛫 3D fleet:** 121 procedural models drawn life size by type — airliners, business jets, helicopters, drones, ships, buses, trams and trains — and every contact swaps from glyph to 3D model as you close in.
+- **🛫 3D fleet:** 122 procedural models drawn life size by type — airliners, business jets, helicopters, drones, ships, buses, trams and trains — and every contact swaps from glyph to 3D model as you close in.
 - **🎨 Reskin reality:** GLSL sensor looks over the normal globe — CRT, NVG, FLIR/thermal, Noir.
 - **🟩 Detection overlay:** Screen-space bounding boxes and IDs on everything in view.
 - **🎖️ Military HUD:** Tactical heads-up display with intelligence-style telemetry.