web: fix A=B/SWAP VFO ops, wire attenuator, TUN button, FNP filter overlay

- Add freq_a command: sets VFO A regardless of active VFO; fixes A=B and
  SWAP when VFO B is active (prev. sent freq_b which overwrote wrong VFO)
- Add pend("freq") to B=A / A=B / SWAP to guard local display during round-trip
- RX step attenuator: HPSDRNetwork.SetStepAtten → bytes 1442/1443 in HP packet;
  WebServer attn command; MainForm FAtten + SyncWebAttn; attSel.onchange in JS
- TUN mode: set_tun WebSocket command wired to ApplyTUN(); toneBtn toggles
  with on/off highlight and pending protection; tuning field in state JSON
- FNP button opens semi-transparent filter overlay (10 buttons, 5×2 grid)
  with mode-appropriate widths (SSB/CW/AM/FM); active filter highlighted;
  cur.filter_bw updated immediately on click so passband redraws within 50ms

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

MainForm.pas

@@ -197,6 +197,7 @@ type
     FHWPTTActive:  Boolean;  // True = hardware PTT нажата
     FMuted:        Boolean;
     FVolume:       Integer;
+    FAtten:        Integer;   // RX step attenuator index: 0=0dB 1=10dB 2=20dB
     FLastSMeter:      Double;
     FSMeterPeak:      Double;    // верхняя граница светлой зоны
     FSMeterMin:       Double;    // нижняя граница светлой зоны
@@ -489,6 +490,9 @@ type
     procedure WebOnCenter(Hz: Double);
     procedure WebOnMOX(On_: Boolean);
     procedure WebOnDrive(V: Integer);
+    procedure WebOnFreqA(Hz: Double);
+    procedure WebOnAttn(Idx: Integer);
+    procedure WebOnTun(On_: Boolean);
     // Synchronize-обёртки (выполняются в UI-потоке)
     procedure SyncWebFreq;
     procedure SyncWebMode;
@@ -512,6 +516,9 @@ type
     procedure SyncWebCenter;
     procedure SyncWebMOX;
     procedure SyncWebDrive;
+    procedure SyncWebFreqA;
+    procedure SyncWebAttn;
+    procedure SyncWebTun;
     // --- CAT callbacks -------------------------------------------------------
     function  CATGetVfoA:       Double;
     function  CATGetVfoB:       Double;
@@ -1091,6 +1098,9 @@ begin
   FWebServer.OnCenter    := WebOnCenter;
   FWebServer.OnMOX       := WebOnMOX;
   FWebServer.OnDrive     := WebOnDrive;
+  FWebServer.OnFreqA     := WebOnFreqA;
+  FWebServer.OnAttn      := WebOnAttn;
+  FWebServer.OnTun       := WebOnTun;
   FWebServer.Start;
   FillChar(FCATLastGlobal, SizeOf(FCATLastGlobal), 0);
   FCATLastGlobal.CATTcpPort := 19090;
@@ -2765,7 +2775,8 @@ begin
       BtnNR.Tag, BtnNB.Tag, BtnSNB.Tag <> 0, BtnANF.Tag <> 0,
       FCenterFreq, FFilter,
       FVfoB, FActiveVfo,
-      FTransmitting, TrkDrive.Position);
+      FTransmitting, TrkDrive.Position,
+      FAtten, FTuning);
 end;
 
 // ===========================================================================
@@ -5204,6 +5215,43 @@ begin
   TrkDrive.Position := FWebSyncInt;
 end;
 
+procedure TMainForm.WebOnFreqA(Hz: Double);
+begin
+  FWebSyncFreq := Hz;
+  FWebSyncM    := SyncWebFreqA;
+  TThread.Synchronize(nil, FWebSyncM);
+end;
+
+procedure TMainForm.SyncWebFreqA;
+begin
+  ApplyVfoA(Round(FWebSyncFreq));
+end;
+
+procedure TMainForm.WebOnAttn(Idx: Integer);
+begin
+  FWebSyncInt := Idx;
+  FWebSyncM   := SyncWebAttn;
+  TThread.Synchronize(nil, FWebSyncM);
+end;
+
+procedure TMainForm.SyncWebAttn;
+begin
+  FAtten := Max(0, Min(2, FWebSyncInt));
+  FNetwork.SetStepAtten(FAtten * 10);
+end;
+
+procedure TMainForm.WebOnTun(On_: Boolean);
+begin
+  FWebSyncBool := On_;
+  FWebSyncM    := SyncWebTun;
+  TThread.Synchronize(nil, FWebSyncM);
+end;
+
+procedure TMainForm.SyncWebTun;
+begin
+  ApplyTUN(FWebSyncBool);
+end;
+
 procedure TMainForm.TrkDriveChange(Sender: TObject);
 begin
   FDriveLevel := CalcDriveByte;