feat(ui-lvgl): SD card as a USB drive, message banner, card format, restart screen

- USB through TinyUSB (ARDUINO_USB_MODE=0) instead of USB-Serial/JTAG: the
  serial port stays, and plugged into a computer (enumerated, the bus not
  suspended -- on battery an unplug only shows as a suspend) the device asks
  "Charge only / USB drive". As a drive the firmware lets go of the card and
  the computer gets its sectors; ejected or unplugged, the device restarts.
- Incoming messages: a banner slides down from under the status bar (icon,
  sender or channel, two lines of the text from history); a tap opens the
  conversation (not while locked), a swipe up dismisses it, not shown for
  the conversation already open. Toasts moved up there too, under the banner
  when both are up; the ones only echoing a switch or a choice are gone.
- Storage > Format card: a popup saying what goes, then Format tapped twice;
  one FAT32 volume over the whole card (readable or not), then a restart.
- A deliberate restart shows a full "Restarting..." screen with the reason
  instead of the screen just freezing.
- The screenshot flash is a thin frame round the edges: a full-screen fade
  redrew all 320x240 each step and tore.

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

examples/companion_radio/ui-lvgl/WifiScreen.h

@@ -189,7 +189,6 @@ void UITask::wifiSetAllowed(bool on) {
     if (mapview::s_dl.active()) mapDownloadStop();
     if (_wifi_scanning) { _wifi_scanning = false; lvport::netEnd(); }
   }
-  showToast(on ? "WiFi on" : "WiFi off", 1500);
   if (_screen == SCR_SETTINGS) {   // the row's subtitle
     lv_obj_t* body = _body;
     int32_t y = body ? lv_obj_get_scroll_y(body) : 0;