feat: QO-100 beacon lock — stabilise LNB drift to NB transponder beacon

Click the beacon on the spectrum; the controller tracks it and continuously
trims the transverter LO so the whole downlink stays put as the LNB drifts.

- BeaconLock.pas: TBeaconTracker scaffold (narrowband NCO/FLL) — kept but no
  longer in the control path (FLL diverged on the suppressed-carrier BPSK
  beacon + Pluto DC offset). Measurement now uses the proven display-FFT path.
- RadioController: FBeaconLockHz folded into XvtrTranslate (on top of LOError).
  MeasureBeaconFFT finds the beacon by POWER-WEIGHTED CENTROID of the lobe
  (BPSK has a suppressed carrier → broad symmetric ~2.4 kHz lobe, not a line;
  a peak-finder jitters, the centroid sits on the carrier). Track position in
  ABSOLUTE display Hz (FBeaconTrackHz) so scrolling the waterfall/centre never
  moves the search window off the beacon. Closed loop: e = tracked - ref,
  d(e)/d(LockHz) = -1 -> LockHz += gain*e; settle cooldown after each correction
  (display-FFT lags the LO retune -> avoids overshoot); deadband 75 Hz +
  centroid/prominence smoothing + lock hysteresis for a steady lock.
  Correction applied only after the user clicks (manual seed), so a crowded
  band can't pull a neighbour to the reference.
- WDSPEngine: SetBeaconTracker + RX-IQ tap (tracker idle now, ~1 check/sample).
- SpectrumView + GL: beacon markers — green = reference (10489.750), orange =
  tracked centroid.
- MainForm: BEACON button (RX block, XVTR-only). Flow: BEACON -> "CLICK BCN"
  -> click beacon -> "L<corr> /<prom>". ServiceBeaconLock driven by MeterTimer.

Reference defaults to the middle BPSK beacon 10489.750. Tested on-air against
Es'hail-2: locks and holds, survives waterfall drag.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

SpectrumView.pas

@@ -73,6 +73,10 @@ type
     // ── Marker ────────────────────────────────────────────────────────────────
     FMarkerActive:  Boolean;
     FMarkerX:       Integer;
+    // ── QO-100 beacon markers (диагностика лока) ──────────────────────────────
+    FBeaconMarkActive: Boolean;
+    FBeaconRefFreq:    Double;   // опорная частота маяка (где ДОЛЖЕН быть)
+    FBeaconTrkFreq:    Double;   // где сидит трекер (NCO) сейчас
     // ── Spectrum buffer ───────────────────────────────────────────────────────
     FSpectrumBuf:       array[0..1023] of Single;
     FSpectrumBufCount:  Integer;
@@ -99,6 +103,7 @@ type
     procedure SetFillSpectrum(V: Boolean);
     procedure DrawSpectrumGradient(const SpPts: array of TPoint; W, H: Integer);
     procedure DrawMarkerLine(C: TCanvas; W, H: Integer);
+    procedure DrawBeaconMarkers(C: TCanvas; W, H: Integer);
     procedure BlendBand(X1, X2, H: Integer; R, G, B, Alpha: Byte);
     procedure CopyGridToSpectrum(W, H: Integer);
     procedure DrawADCOverloadOverlay(C: TCanvas; W, H: Integer);
@@ -182,6 +187,10 @@ type
     property MarkerActive: Boolean read FMarkerActive write SetMarkerActive;
     property MarkerX:      Integer read FMarkerX      write SetMarkerX;
 
+    // QO-100 beacon-маркеры: опорная частота (зелёная) + позиция трекера (оранж).
+    // Спектр перерисовывается каждый кадр, поэтому отдельный invalidate не нужен.
+    procedure SetBeaconMarkers(Active: Boolean; RefHz, TrkHz: Double);
+
     // ── S-метр ────────────────────────────────────────────────────────────────
     property LastSMeter:   Double  read GetLastSMeter   write SetLastSMeter;
     property SMeterPeak:   Double  read GetSMeterPeak   write SetSMeterPeak;
@@ -485,6 +494,32 @@ begin
     C.TextOut(MX - 4 - C.TextWidth(MarkerLbl), 4, MarkerLbl);
 end;
 
+procedure TSpectrumView.SetBeaconMarkers(Active: Boolean; RefHz, TrkHz: Double);
+begin
+  FBeaconMarkActive := Active;
+  FBeaconRefFreq    := RefHz;
+  FBeaconTrkFreq    := TrkHz;
+end;
+
+procedure TSpectrumView.DrawBeaconMarkers(C: TCanvas; W, H: Integer);
+// Две вертикали: опорная частота маяка (зелёная пунктир) и текущая позиция
+// трекера (оранжевая сплошная). Расхождение видно глазом → понятно, на пик
+// сел трекер или на шум.
+  procedure Vline(FreqHz: Double; Col: TColor; Style: TPenStyle);
+  var x: Integer;
+  begin
+    if FSpanHz <= 0 then Exit;
+    x := Round((FreqHz - (FCenterFreq - FSpanHz / 2)) / FSpanHz * W);
+    if (x < 0) or (x >= W) then Exit;
+    C.Pen.Color := Col; C.Pen.Width := 1; C.Pen.Style := Style;
+    C.MoveTo(x, 0); C.LineTo(x, H);
+  end;
+begin
+  Vline(FBeaconRefFreq, clLime,            psDot);     // где маяк ДОЛЖЕН быть
+  Vline(FBeaconTrkFreq, TColor($000AA5FF), psSolid);   // где сидит трекер (оранж)
+  C.Pen.Style := psSolid;
+end;
+
 procedure TSpectrumView.BlendBand(X1, X2, H: Integer; R, G, B, Alpha: Byte);
 var
   Y, X, InvA: Integer;
@@ -940,6 +975,7 @@ begin
   end;
 
   if FMarkerActive then DrawMarkerLine(C, W, H);
+  if FBeaconMarkActive then DrawBeaconMarkers(C, W, H);
   DrawADCOverloadOverlay(C, W, H);
   if Assigned(FSampleRateOverlay) then
     FSampleRateOverlay.DrawOverlay(FSpectrumBitmap, C, W, H);