Subscribes to saltybot/phone/gps (JSON: {ts, lat, lon, alt_m,
accuracy_m, speed_ms, bearing_deg, provider}) and renders a blue
Leaflet marker + blue breadcrumb trail alongside the robot's
orange/cyan marker. Status bar now shows PHONE badge with stale
detection. Sidebar adds phone lat/lon/speed/accuracy/provider section.
Clear button resets both trails.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>