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.

public/models/fleet/catalog.json

@@ -1785,6 +1785,25 @@
   "tris": 1172,
   "icon": "heli"
  },
+ "radio_mast": {
+  "category": "other",
+  "file": "other/radio_mast.glb",
+  "min": [
+   -0.7,
+   -0.815,
+   0.0
+  ],
+  "max": [
+   1.2,
+   0.815,
+   11.8
+  ],
+  "length": 1.9,
+  "beam": 1.63,
+  "clearance": 0.0,
+  "tris": 940,
+  "icon": "vehicle"
+ },
  "regional_dmu": {
   "category": "transit",
   "file": "transit/regional_dmu.glb",