feat(companion): repeater mode, radio presets, and manual RF tuning in Settings

Settings > Radio gains:
- Repeater toggle — turns on flood forwarding (client_repeat) on the current
  operating frequency, with loop-detection and an 8-hop advert cap ported
  from simple_repeater's allowPacketForward.
- Packet pool bumped 16->32: forwarding's queued retransmits were starving
  Dispatcher::checkRecv()'s allocNew(), silently dropping incoming DMs and
  channel messages while repeating.
- Preset picker (16 community-suggested region presets) plus manual
  Freq/SF/BW/CR fields for fine-tuning. Freq bounds come from the radio
  driver's own RadioLib-validated range (SX1262: 150-960MHz) instead of a
  guessed sanity bound.
- Save current radio settings as a named user preset (4 persisted slots),
  alongside the built-in list.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

examples/companion_radio/ui-new/UITask.cpp

@@ -2093,6 +2093,11 @@ void UITask::applyApc() {
   the_mesh.applyApc();   // (re)initialise Adaptive Power Control from prefs
 }
 
+void UITask::applyRadioParams() {
+  if (_node_prefs == NULL) return;
+  radio_driver.setParams(_node_prefs->freq, _node_prefs->bw, _node_prefs->sf, _node_prefs->cr);
+}
+
 void UITask::applyBrightness() {
   if (_display != NULL && _node_prefs != NULL) {
     _display->setBrightness(_node_prefs->display_brightness);