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/UITask.h

@@ -135,6 +135,7 @@ public:
   void setKeyboardAlphabets(int main_idx, int alt_sel);
   void openChannel(uint8_t channel_idx);
   void openDM(const uint8_t* pub_key);
+  void bannerOpen();   // the message banner tapped: its conversation
   void back();
   void sendFromCompose();
   void setKeyboardVisible(bool show);
@@ -256,6 +257,10 @@ public:
   void storageClearHistory();
   void storageLiveCap(int idx);
   void storageClearLive();
+  void storageFormatAsk();    // Storage > Format card: the popup (first confirmation)
+  void storageFormatTap(bool go);   // its buttons: Format twice (the second confirmation), or Cancel
+  void usbPoll();              // a computer plugged in: offer the SD card as a USB drive
+  void usbTap(bool drive);     // that popup's buttons
   bool locked() const;
   void pinKey(const char* key);        // the lock screen's keypad
   void pinSetupPopup();                // Settings > Display & power > Screen PIN