feat(map): packet flow - what the radio hears, as lines between nodes

Every packet heard runs from its origin through the repeaters with a
position to this device; a packet sent is a ring. ui-core/PacketFlow.h
resolves them (UiCore::flow, MyMesh logRx/logTx -> Listener). ui-lvgl
draws them on the map's marker layer and repaints only their area while
they move; ui-new draws the last minute on the Nodes map ("Flow" in its
options). Setting: Map options > On the map > Packet flow, CLI map.flow.
Off by default. Sim-checked only.

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

examples/companion_radio/ui-lvgl/UITask.h

@@ -131,6 +131,7 @@ public:
   void routeMapUndo();
   void routeMapFrame();
   void buildRouteBar(lv_obj_t* body);
+  void mapFlowTick();
   void mapDownloadPopup();
   // Map areas (MapAreas.h)
   void areaBuildLayer(lv_obj_t* body);
@@ -366,6 +367,7 @@ public:
   void openAdminFor(const ContactInfo& ci, bool from_picker) { (void)from_picker; openAdmin(ci.id.pub_key); }
   void openRouteFor(const uint8_t* pub_key) { showRoute(pub_key); }
   void openMessagesList() { showChats(); }   // sim harness
+  bool openNodesMap() { openMap(false); return true; }   // sim harness
 
 private:
   enum Screen : uint8_t { SCR_HOME, SCR_CHATS, SCR_CONTACTS, SCR_THREAD, SCR_SETTINGS, SCR_NEARBY, SCR_NODE, SCR_MAP, SCR_WIFI, SCR_SETTINGS_NAV, SCR_CLOCK, SCR_RADIO, SCR_CHANNEL_EDIT, SCR_ADMIN, SCR_BOT, SCR_DIAG, SCR_COMPASS, SCR_SCOPES, SCR_REPEATER, SCR_MELODY, SCR_QUICK, SCR_ADMIN_PICK, SCR_OTA, SCR_STORAGE, SCR_GPS, SCR_BATT, SCR_ROUTE, SCR_ROUTE_PICK };
@@ -641,6 +643,7 @@ private:
   lv_obj_t* _route_keep_btn = nullptr;    // header: Keep (accent while kept)
   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
   bool      _route_pick = false;         // the nodes map taps repeaters into the route
   lv_obj_t* _route_bar = nullptr;
   lv_obj_t* _route_lbl = nullptr;