Fix TX sequencing: PTT after Alex relay, SEQ error on startup

- Separate FPTTActive from FIsTransmitting so PTT bit in HP packet
  can be sent as a second packet after Alex bit27 (T/R relay) is set,
  matching Thetis behaviour: relay switches first, then PTT=1
- On TX stop: PTT=0 first, then Alex switches back to RX
- Add SendPTT(Active) method to THPSDRNetwork
- Reset FSeqHP to 0 in SetRunAndFreq(Run=True) to eliminate HP SEQ
  ERROR caused by intermediate SendFullHP calls before Run=1 packet
- RebuildXvtrButtons: use dynamic BtnH/RowH/MaxBottom instead of
  hardcoded px values so XVTR buttons scale correctly on HiDPI

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

MainForm.pas

@@ -4571,7 +4571,8 @@ begin
     FNetwork.ClearDUCIQQueue;
     FNetwork.UpdateState(XvtrTranslate(FCenterFreq), XvtrTranslate(ActiveTXFreqHz), FDriveLevel,
                          True, True, True);
-    FNetwork.SendFullHP;
+    FNetwork.SendFullHP;    // 1й пакет: Alex bit27=1 (T/R relay), drive — без PTT
+    FNetwork.SendPTT(True); // 2й пакет: PTT=1 после переключения реле
   end;
   if FWDSPReady then
   begin
@@ -4615,10 +4616,11 @@ begin
   end;
   if (not FTransmitting) and FNetwork.Connected and FNetwork.Running then
   begin
+    FNetwork.SendPTT(False); // 1й пакет: PTT=0 — сначала снимаем PTT
     FNetwork.UpdateState(XvtrTranslate(FCenterFreq), XvtrTranslate(ActiveTXFreqHz), FDriveLevel,
-                         FTransmitting, True, True);
+                         False, True, True);
     FNetwork.ClearDUCIQQueue;
-    FNetwork.SendFullHP;
+    FNetwork.SendFullHP;     // 2й пакет: Alex bit27=0 (T/R relay RX), drive=0
   end;
 end;
 
@@ -5632,11 +5634,9 @@ begin
 end;
 
 procedure TMainForm.RebuildXvtrButtons;
-const
-  BTN_H_LOC = 24;
 var
   i, Pos, XvtrRows: Integer;
-  W:      Integer;
+  W, BtnH, RowH, MaxBottom: Integer;
   B:      TFlatButton;
   Cap:    string;
 begin
@@ -5648,6 +5648,21 @@ begin
       BtnXvtrBand[i] := nil;
     end;
   if PanelBands = nil then Exit;
+
+  // Измеряем фактический bottom последнего ряда обычных кнопок BAND
+  // (уже отмасштабированы LCL при показе формы)
+  MaxBottom := 0;
+  BtnH := 0;
+  for i := 0 to BAND_COUNT - 1 do
+    if BtnBand[i] <> nil then
+    begin
+      if BtnBand[i].Top + BtnBand[i].Height > MaxBottom then
+        MaxBottom := BtnBand[i].Top + BtnBand[i].Height;
+      BtnH := BtnBand[i].Height;
+    end;
+  if BtnH = 0 then BtnH := MulDiv(24, Screen.PixelsPerInch, 96);
+  RowH := BtnH + 3;  // шаг ряда: высота кнопки + 3px зазор (как 27=24+3 при 1x)
+
   W := (PanelBands.Width - 6) div 6;
   Pos := 0;   // позиция среди enabled слотов
   for i := 0 to CFG_XVTR_COUNT - 1 do
@@ -5660,20 +5675,23 @@ begin
       B.Parent  := PanelBands;
       B.Caption := Cap;
       B.Left    := 2 + (Pos mod 6) * W;
-      B.Top     := 16 + (2 + (Pos div 6)) * 27;
+      B.Top     := MaxBottom + 4 + (Pos div 6) * RowH;
       B.Width   := W - 2;
-      B.Height  := BTN_H_LOC;
+      B.Height  := BtnH;
       B.OnClick := BtnXvtrBandClick;
       B.Tag     := -(i + 1);   // отрицательное значение = XVTR индекс
       BtnXvtrBand[i] := B;
       StyleButton(B, i = FCurrentXvtr);
       Inc(Pos);
     end;
-  // Динамически подгоняем высоту PanelBands под реальное число XVTR-рядов
+  // Динамически подгоняем высоту PanelBands под реальное содержимое
   if Pos = 0 then XvtrRows := 0
   else if Pos <= 6 then XvtrRows := 1
   else XvtrRows := 2;
-  PanelBands.Height := 74 + XvtrRows * 27;
+  if XvtrRows = 0 then
+    PanelBands.Height := MaxBottom + 6
+  else
+    PanelBands.Height := MaxBottom + 4 + XvtrRows * RowH + 6;
   RelayoutBelowBands;
 end;