feat: QO-100 beacon lock in web UI + headless daemon

Mirror the desktop QO-100 beacon lock into the web interface and make it
work in the headless daemon.

Backend:
- WebServer: set_beacon/beacon_seed commands (+OnBeacon/OnBeaconSeed
  events), beacon state fields, SetBeaconStatus, and beacon_visible/on/
  text/ref_hz/track_hz in BuildStateJson. beacon_seed carries 'frac'
  (0..1 click position); absolute Hz is computed controller-side from
  live FCenterFreq/FSpanHz (mirrors desktop PixelToFreq).
- WebAdapter: OnBeacon->SetBeaconLock, OnBeaconSeed->BeaconSeedAtHz;
  PushState mirrors compact status (matches MainForm.BeaconStatusText)
  into the PLL status cell when visible (Pluto + active XVTR).
- MainForm/ewsdrd: wire the two callbacks.
- ewsdrd: call ServiceBeaconLock in the main loop @~10Hz (FRunning+
  FWDSPReady gated). Without this the lock loop never ran headless.

Frontend (WebPageHtml):
- BCN button (visible only on Pluto+XVTR), highlighted while locked.
- Seed-on-mousedown with immediate return (like desktop FormMouseDown):
  no drag/set_center so the gesture never moves the center / tears IQ.
  Armed (first click after BCN) or Shift, mirroring desktop arm/Shift.
- PLL status cell shows beacon status (field-7 parity with desktop).
- Ref (green) + tracked (orange) beacon markers on spectrum/waterfall.

Known issue (unresolved): after lock the beacon can slowly drift off and
drop to "BCN sync". Suspected residual-sign anti-drift or retune-timing
on the web/daemon path; needs on-air diagnostics. See memory
project_web_beacon for the investigation state.

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

WebServer.pas

@@ -151,6 +151,9 @@ type
   // XVTR-band: web клиент кликнул кнопку трансвертера (Idx 0..CFG_XVTR_COUNT-1).
   // Idx=-1 — выход в HF.
   TWebCmdXvtrBand  = procedure(Idx: Integer) of object;
+  // QO-100 beacon lock: вкл/выкл лок и наведение (клик по маяку, доля 0..1 по ширине).
+  TWebCmdBeacon     = procedure(On_: Boolean) of object;
+  TWebCmdBeaconSeed = procedure(Frac: Double) of object;
   // Активность web-клиента изменилась (подключился/отключился последний клиент).
   // Хозяин зеркалит это в ядро (FController.FWebClientActive) для выбора mic-source.
   TWebClientActiveEvent = procedure(Active: Boolean) of object;
@@ -317,6 +320,16 @@ type
     FTXText:      string;
     FSeqText:     string;
 
+    // QO-100 beacon lock (Pluto в трансвертере). Зеркалится в state как
+    // beacon_visible/on/text/ref_hz/track_hz; команды set_beacon/beacon_seed.
+    FBeaconVisible: Boolean;       // кнопка/статус активны (Pluto + XVTR)
+    FBeaconOn:      Boolean;       // лок включён (подсветка кнопки)
+    FBeaconText:    string;        // компактный статус (ячейка PLL, как десктоп)
+    FBeaconRefHz:   Double;        // опорная частота маяка (маркер)
+    FBeaconTrackHz: Double;        // измеренная частота маяка (маркер)
+    FOnBeacon:      TWebCmdBeacon;
+    FOnBeaconSeed:  TWebCmdBeaconSeed;
+
     FWebClientActive: Boolean;
     FOnClientActiveChanged: TWebClientActiveEvent;
 
@@ -400,6 +413,11 @@ type
     procedure SetRatePresets(const ARates: array of Integer);
     procedure SetBands(const ANames: array of string; const AFreqs: array of Double);
     procedure SetFreqRange(AMin, AMax: Double);
+    // QO-100 beacon lock: зеркало статуса в state (зовётся из PushState хозяина).
+    procedure SetBeaconStatus(AVisible, AOn: Boolean; const AText: string;
+                              ARefHz, ATrackHz: Double);
+    property OnBeacon:     TWebCmdBeacon     read FOnBeacon     write FOnBeacon;
+    property OnBeaconSeed: TWebCmdBeaconSeed read FOnBeaconSeed write FOnBeaconSeed;
     property OnSpan:   TWebCmdSpan   read FOnSpan   write FOnSpan;
     property OnVolume: TWebCmdVolume read FOnVolume write FOnVolume;
     property OnWfAGC:  TWebCmdWfAGC  read FOnWfAGC  write FOnWfAGC;
@@ -542,6 +560,11 @@ begin
   FBandIdx    := 5;
   FCurrentXvtr  := -1;
   FFreqMhzDigits := 3;
+  FBeaconVisible := False;
+  FBeaconOn      := False;
+  FBeaconText    := '';
+  FBeaconRefHz   := 0;
+  FBeaconTrackHz := 0;
   SetLength(FXvtrBands, 0);
   // Bootstrap-набор рейтов (до connect): хост перезапишет под бэкенд (HPSDR/Pluto).
   SetRatePresets([48000, 96000, 192000, 384000, 768000, 1536000]);
@@ -566,6 +589,21 @@ begin
   end;
 end;
 
+procedure TWebServer.SetBeaconStatus(AVisible, AOn: Boolean; const AText: string;
+  ARefHz, ATrackHz: Double);
+begin
+  FStateLock.Enter;
+  try
+    FBeaconVisible := AVisible;
+    FBeaconOn      := AOn;
+    FBeaconText    := AText;
+    FBeaconRefHz   := ARefHz;
+    FBeaconTrackHz := ATrackHz;
+  finally
+    FStateLock.Leave;
+  end;
+end;
+
 procedure TWebServer.SetDeviceList(const ADevices: TWebDeviceArray);
 var i: Integer;
 begin
@@ -1444,6 +1482,20 @@ begin
     FStateLock.Enter; FTuning := On_; FStateLock.Leave;
     if Assigned(FOnTun) then FOnTun(On_);
   end
+  else if Cmd = 'set_beacon' then
+  begin
+    On_ := JsonGetBool(Json, 'on', FBeaconOn);
+    FStateLock.Enter; FBeaconOn := On_; FStateLock.Leave;
+    if Assigned(FOnBeacon) then FOnBeacon(On_);
+  end
+  else if Cmd = 'beacon_seed' then
+  begin
+    // frac = доля позиции клика по ширине спектра (0..1). Абсолютную display-частоту
+    // считает контроллер из ЖИВЫХ FCenterFreq/FSpanHz (как десктоп PixelToFreq) —
+    // клиентский localCenter может отставать при ретюне LO во время лока.
+    HzF := JsonGetFloat(Json, 'frac', -1);
+    if (HzF >= 0) and Assigned(FOnBeaconSeed) then FOnBeaconSeed(HzF);
+  end
   else if Cmd = 'freq_a' then
   begin
     HzF := JsonGetFloat(Json, 'hz', FFreq);
@@ -1664,7 +1716,9 @@ begin
 	      '"pll_text":"%s","rx_text":"%s","tx_text":"%s","seq_text":"%s",' +
 	      '"xvtr_current":%d,"xvtr_bands":%s,"freq_mhz_digits":%d,' +
 	      '"fmstep_idx":%d,"devices":%s,"rate_presets":%s,"bands":%s,' +
-	      '"freq_min":%.0f,"freq_max":%.0f}',
+	      '"freq_min":%.0f,"freq_max":%.0f,' +
+	      '"beacon_visible":%s,"beacon_on":%s,"beacon_text":"%s",' +
+	      '"beacon_ref_hz":%.0f,"beacon_track_hz":%.0f}',
       [FFreq, FVfoB, FActiveVfo,
        FMode, MODE_N[FMode mod 8],
        FFilterIdx, FFilterBW,
@@ -1694,7 +1748,10 @@ begin
 	       JsonEscape(FTXText), JsonEscape(FSeqText),
 	       FCurrentXvtr, XvtrJson, FFreqMhzDigits,
        FFMStepIdx, DevJson, RateJson, BandJson,
-       FFreqMin, FFreqMax
+       FFreqMin, FFreqMax,
+       BoolToStr(FBeaconVisible, 'true', 'false'),
+       BoolToStr(FBeaconOn,      'true', 'false'),
+       JsonEscape(FBeaconText), FBeaconRefHz, FBeaconTrackHz
       ], FS);
   finally
     FStateLock.Leave;