fn_live_positions now emits 'vehicle_type' (devices.vehicle_models) and
'fleet_segment' (reporting.fn_fleet_segment) in each GeoJSON feature so FleetNow
can give specialist vehicles (Crane/Motorbike/Pick-Up) their own marker icons.
Additive only — no signature change, STABLE function read immediately by
dashboard_api (no redeploy). Function body reproduced verbatim from prod via
pg_get_functiondef plus the two new properties.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>