feat(map): packet flow shows all traffic - kinds in colours, a legend, its own nodes

- Every packet heard is drawn, by kind in fixed colours: advert, DM,
  channel, request, ack, other, sent. One that can't be placed on the map
  is a ring at your own position.
- A legend pill at the top counts each kind over the last minute.
- On a map without node markers, a flow brings its own nodes (a dot and
  the name), fading with it.
- Copies of one packet (the same packet hash) share one fade, so a path
  goes out as a whole, not segment by segment.
- 32 flows kept on ESP32 (12 on nRF).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

examples/companion_radio/ui-lvgl/UITask.h

@@ -656,6 +656,7 @@ private:
   uint32_t  _route_shown = 0xFFFFFFFF;     // what routeRebuild() drew (routeSig())
   uint32_t  _next_route_ms = 0;
   uint32_t  _next_flow_ms = 0;            // the map's packet flow repaint
+  uint8_t   _flow_legend_tick = 0;        // its legend, every 10th repaint
   bool      _route_pick = false;         // the nodes map taps repeaters into the route
   lv_obj_t* _route_bar = nullptr;
   lv_obj_t* _route_lbl = nullptr;