fix(radio): drop companion FEM wiring; wire t096 + tracker_v2 FEM overrides

companion_radio has its own NodePrefs without radio_fem_rxgain (matching
upstream, which doesn't wire companion either), so the startup call added in
e905451d broke every companion build:
  MyMesh.cpp:973: error: 'struct NodePrefs' has no member named 'radio_fem_rxgain'
It went unnoticed behind the pre-existing companion build failures.

Also port upstream's FEM LNA overrides for heltec_t096 and heltec_tracker_v2
verbatim (board overrides + isLNAEnabled/const getters), so all three boards
upstream wires now match instead of reporting unsupported. Both variant files
compile; those targets still fail overall on the pre-existing non-observer
MQTT-source build-config issue (unchanged with this work stashed).

variants/heltec_tracker_v2/HeltecTrackerV2Board.cpp

@@ -82,3 +82,21 @@ void HeltecTrackerV2Board::begin() {
   const char* HeltecTrackerV2Board::getManufacturerName() const {
     return "Heltec Tracker V2";
   }
+
+  bool HeltecTrackerV2Board::setLoRaFemLnaEnabled(bool enable) {
+    if (!loRaFEMControl.isLnaCanControl()) {
+      return false;
+    }
+
+    loRaFEMControl.setLNAEnable(enable);
+    loRaFEMControl.setRxModeEnable();
+    return true;
+  }
+
+  bool HeltecTrackerV2Board::canControlLoRaFemLna() const {
+    return loRaFEMControl.isLnaCanControl();
+  }
+
+  bool HeltecTrackerV2Board::isLoRaFemLnaEnabled() const {
+    return loRaFEMControl.isLNAEnabled();
+  }