Fix supply voltage: apply PCB voltage dividers and read correct ADC source

Protocol Appendix A documents only the ADC reference voltage constant;
the PCB voltage divider must also be applied (from Thetis source):
- Boards 1-3 (Hermes/Angelia): ×(4.7+0.82)/0.82 ≈ 6.73, Vref=3.3V
- Board 5 (Orion MkII): ×(22+1)/1.1 ≈ 20.9, Vref=5.0V

For board type 5, supply voltage is measured via UserADC0 (bytes 57-58),
not the supply_volts field (bytes 49-50), matching Thetis behaviour.

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

MainForm.pas

@@ -2461,8 +2461,16 @@ begin
   ExcPwr  := (Status.ExciterPwr0Hi shl 8) or Status.ExciterPwr0Lo;
   FwdPwr  := (Status.FwdPwrAlex0Hi shl 8) or Status.FwdPwrAlex0Lo;
   RevPwr  := (Status.RevPwrAlex0Hi shl 8) or Status.RevPwrAlex0Lo;
-  SupplyV := ADCToSupplyVolts((Status.SupplyVoltsHi shl 8) or Status.SupplyVoltsLo,
-               FNetwork.Device.BoardType);
+  // Board 5 (Orion MkII) measures supply voltage via UserADC0 (bytes 57-58),
+  // not the supply_volts field (bytes 49-50) — matching Thetis behaviour.
+  if FNetwork.Device.BoardType = 5 then
+    SupplyV := ADCToSupplyVolts(
+                 (Status.UserADC0Hi shl 8) or Status.UserADC0Lo,
+                 FNetwork.Device.BoardType)
+  else
+    SupplyV := ADCToSupplyVolts(
+                 (Status.SupplyVoltsHi shl 8) or Status.SupplyVoltsLo,
+                 FNetwork.Device.BoardType);
   // FLastSMeter обновляется только из WDSP (GetSMeterDBm) в SpectrumTimerTick —
   // ExciterPwr это мощность TX, не уровень принятого сигнала.
   FwdW := ADCToWatts100(FwdPwr);