feat: flashlight - the whole screen white at full brightness

L2: a Flashlight app on Home (a lightbulb icon added to the fonts): a
white layer over everything, the backlight at 100 %, no auto-off; a tap,
the side or the top button puts it away and the brightness back.
L1: Tools > System > Flashlight, the whole OLED lit at full contrast
until a key. Not on e-ink.

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

examples/companion_radio/ui-new/FlashlightScreen.h

@@ -0,0 +1,26 @@
+#pragma once
+// Tools › Flashlight: the whole panel lit at full brightness, kept on (no
+// auto-off) until a key. Not on e-ink, which gives no light. Leaving it, by
+// a key or anything that changes the screen, puts the brightness back
+// (UITask::setCurrScreen).
+// Included by UITask.cpp.
+
+class FlashlightScreen : public UIScreen {
+  UITask* _task;
+
+public:
+  FlashlightScreen(UITask* task) : _task(task) {}
+
+  int render(DisplayDriver& display) override {
+    display.setBrightness(4);
+    display.setColor(DisplayDriver::LIGHT);
+    display.fillRect(0, 0, display.width(), display.height());
+    return 1000;
+  }
+
+  bool handleInput(char c) override {
+    (void)c;
+    _task->leaveTool();
+    return true;
+  }
+};