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>

SpectrumViewOpengl.pas

@@ -75,6 +75,7 @@ type
     procedure DrawAGCLines(W, H: Integer; DBmax, InvRange: Double);
     procedure DrawSpectrumCurve(W, H: Integer; DBmax, InvRange: Double);
     procedure DrawMarker(W, H: Integer);
+    procedure DrawBeaconMarkersGL(W, H: Integer);
     procedure DrawADCOverlay(W, H: Integer);
     procedure DrawCachedOverlays(W, H: Integer);
     function FormatFreqGL(Hz: Double): string;
@@ -656,6 +657,21 @@ begin
   else DrawTexture(FMarkerLabelTex, MX - 4 - FMarkerLabelTex.W, 4);
 end;
 
+procedure TSpectrumViewOpenGL.DrawBeaconMarkersGL(W, H: Integer);
+// QO-100 beacon-маркеры: опорная частота (зелёная) + позиция трекера (оранж).
+  procedure Vline(FreqHz: Double; Col: TColor);
+  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;
+    DrawLine(x, 0, x, H, Col, 1, False);
+  end;
+begin
+  Vline(FBeaconRefFreq, clLime);             // где маяк ДОЛЖЕН быть
+  Vline(FBeaconTrkFreq, TColor($000AA5FF));  // где сидит трекер (оранж)
+end;
+
 procedure TSpectrumViewOpenGL.DrawADCOverlay(W, H: Integer);
 var
   B: TBitmap;
@@ -781,6 +797,7 @@ begin
   DrawAGCLines(W, H, DBmax, InvRange);
   DrawSpectrumCurve(W, H, DBmax, InvRange);
   DrawMarker(W, H);
+  if FBeaconMarkActive then DrawBeaconMarkersGL(W, H);
   DrawADCOverlay(W, H);
   DrawCachedOverlays(W, H);