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/MyMesh.h

@@ -152,6 +152,7 @@ protected:
   uint8_t getExtraAckTransmitCount() const override;
   bool filterRecvFloodPacket(mesh::Packet* packet) override;
   bool allowPacketForward(const mesh::Packet* packet) override;
+  bool isRepeatLooped(const mesh::Packet* packet) const;
 
   void sendFloodScoped(const TransportKey& scope, mesh::Packet* pkt, uint32_t delay_millis);
   void sendFloodScoped(const ContactInfo& recipient, mesh::Packet* pkt, uint32_t delay_millis=0) override;