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>

WDSPEngine.pas

@@ -25,7 +25,7 @@ interface
 
 uses
   Classes, SysUtils, Math, SyncObjs,
-  WDSP;
+  WDSP, BeaconLock;
 
 const
   // WDSP mode integers (нет именованных констант в WDSP.pas)
@@ -292,6 +292,7 @@ type
     FMuted:      Boolean;
     FVolume:     Double;
     FLastError:  string;
+    FBeaconTracker: TBeaconTracker;   // QO-100 beacon lock (НЕ владеем; см. контроллер)
 
     function  ModeToWDSP(Mode: Integer): Integer;
     procedure ApplyDefaultFilter;
@@ -354,6 +355,9 @@ type
     procedure UpdateAGCLines(SpectrumW: Integer);  // читает hang/thresh из WDSP для линии на спектре
     procedure SetSpectrumWidth(W: Integer);         // обновляет FLastSpectrumW для корректных AGC линий
     procedure SetShift(ShiftHz: Double);  // CTUN NCO сдвиг
+    // QO-100 beacon lock: трекер кормится RX-IQ из DSP-потока. Владелец —
+    // контроллер; движок лишь подаёт сэмплы и сообщает sample rate.
+    procedure SetBeaconTracker(T: TBeaconTracker);
     procedure SetNRMode(Mode: Integer);
     procedure SetNR(Enable: Boolean);
     procedure SetNBMode(Mode: Integer);
@@ -1119,6 +1123,7 @@ begin
   // Обновляем параметры
   FSampleRate   := NewRate;
   FBufSize      := FAudioBufSize * NewRate div FAudioRate;
+  if FBeaconTracker <> nil then FBeaconTracker.Configure(FSampleRate);
 
   // Перераспределяем буферы под новый размер
   SetLength(FRXIn,    FBufSize * 2);
@@ -1213,6 +1218,11 @@ begin
 
     FeedDisplaySample(IR * SCALE, QR * SCALE);
 
+    // QO-100 beacon lock: тот же baseband-IQ @ FSampleRate (трекер сам
+    // мгновенно выходит, если лок не активен — стоимость ~1 проверка/сэмпл).
+    if FBeaconTracker <> nil then
+      FBeaconTracker.Feed(IR * SCALE, QR * SCALE);
+
     FRXAccI[FRXAccPos] := IR * SCALE;
     FRXAccQ[FRXAccPos] := QR * SCALE;
     Inc(FRXAccPos);
@@ -1371,6 +1381,12 @@ begin
   UpdateAGCLines(FLastSpectrumW);
 end;
 
+procedure TWDSPEngine.SetBeaconTracker(T: TBeaconTracker);
+begin
+  FBeaconTracker := T;
+  if (T <> nil) and (FSampleRate > 0) then T.Configure(FSampleRate);
+end;
+
 procedure TWDSPEngine.SetShift(ShiftHz: Double);
 begin
   FShiftHz := ShiftHz;