feat(l2,core): battery curve editor and an L2 feedback round

- Battery curve: NodePrefs batt_curve_mv[11] (voltage at 0..100 %, all
  zeros = built-in LiPo curve, sentinel 0xC0DE0032). ui-core/Battery.h
  uses it for every percentage. L1: Settings > System > Batt curve list
  (Left/Right 10 mV, Reset); L2: Settings > Power > Battery curve chart
  with draggable points and a line at the cell's voltage.
- L2: the Nodes map is the full navigation map plus the nodes, Back
  returns to Nodes; the favourite button is lit while it is one; pinning
  to the Home dial uses a thumbtack (fonts regenerated); minimap dots
  follow the accent; arranging tiles shows where they land while dragging;
  emoji row in Diagnostics > Font.
- Sim hooks: sim_open nodesmap / accent@N / homeedit / battcurve.

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

examples/companion_radio/ui-new/UITask.cpp

@@ -177,6 +177,7 @@ static void fmtAlt(char* buf, int n, float meters, bool imperial) {
 #include "NearbyScreen.h"
 #include "DashboardConfigScreen.h"
 #include "AutoAdvertScreen.h"
+#include "BatteryCurveScreen.h"
 #include "LiveShareScreen.h"
 #include "LocatorScreen.h"
 #include "TrailScreen.h"
@@ -1623,6 +1624,7 @@ void UITask::begin(DisplayDriver* display, SensorManager* sensors, NodePrefs* no
   _sensors = sensors;
   _node_prefs = node_prefs;
   _kb.prefs = node_prefs;
+  if (node_prefs) battery::useCurve(node_prefs->batt_curve_mv);   // Settings > Battery curve
   uint32_t aoff = autoOffMillis();
   _auto_off = millis() + (aoff > 0 ? aoff : AUTO_OFF_MILLIS);
 
@@ -1719,6 +1721,7 @@ void UITask::begin(DisplayDriver* display, SensorManager* sensors, NodePrefs* no
   nearby_screen = new NearbyScreen(this);
   dashboard_config = new DashboardConfigScreen(this, node_prefs);
   auto_advert_screen = new AutoAdvertScreen(this, node_prefs);
+  batt_curve_screen = new BatteryCurveScreen(this, node_prefs);
   live_share_screen = new LiveShareScreen(this, node_prefs);
   locator_screen  = new LocatorScreen(this, node_prefs);
   trail_screen       = new TrailScreen(this, &_core->trail.store());
@@ -1853,6 +1856,7 @@ void UITask::gotoMapScreen() {
 
 void UITask::gotoLocatorScreen()    { setCurrScreen(locator_screen); }
 void UITask::gotoAutoAdvertScreen() { setCurrScreen(auto_advert_screen); }
+void UITask::gotoBatteryCurve() { setCurrScreen(batt_curve_screen); }
 
 bool UITask::startPing(const uint8_t* pub_key) {
   PingEngine::StartResult r = _core->ping.start(pub_key);