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>

ewsdrd.lpr

@@ -167,6 +167,7 @@ begin
   FWeb.OnCtun   := @FWebAd.OnCtun;     FWeb.OnActiveVfo := @FWebAd.OnActiveVfo;
   FWeb.OnMOX    := @FWebAd.OnMOX;      FWeb.OnTun    := @FWebAd.OnTun;
   FWeb.OnFMStep := @FWebAd.OnFMStep;   FWeb.OnXvtrBand := @FWebAd.OnXvtrBand;
+  FWeb.OnBeacon := @FWebAd.OnBeacon;   FWeb.OnBeaconSeed := @FWebAd.OnBeaconSeed;
   FWeb.OnWebMic := @FWebAd.OnMic;
   FWeb.OnClientActiveChanged := @FWebAd.OnClientActiveChanged;
   // Host-coupled (lifecycle) — на демон-хост (маршалит в главный поток).
@@ -409,7 +410,7 @@ var
   WebCfg: TWebSettings;
   Dev: THPSDRDevice;
   AutoDev: TSavedDevice;
-  lastPush, nowMs: QWord;
+  lastPush, lastBeacon, nowMs: QWord;
 begin
   FCtrl.FSettings.LoadWebSettings(WebCfg);
   if not FWeb.Start then
@@ -444,10 +445,19 @@ begin
     Log('No autostart device — waiting for web connect.');
 
   lastPush := GetTickCount64;
+  lastBeacon := lastPush;
   while FRunning do
   begin
     CheckSynchronize(PUSH_INTERVAL_MS);   // исполняет очередь Invoke + ждёт до 50мс
     nowMs := GetTickCount64;
+    // QO-100 beacon lock — одна итерация контура @~10 Гц (как GUI MeterTimer). No-op
+    // если лок выключен. Без этого лок маяка не работал бы в headless-демоне.
+    if nowMs - lastBeacon >= 100 then
+    begin
+      if FCtrl.FRunning and FCtrl.FWDSPReady then
+        FCtrl.ServiceBeaconLock;
+      lastBeacon := nowMs;
+    end;
     if nowMs - lastPush >= PUSH_INTERVAL_MS then
     begin
       // S-метр приходит из WDSP (не из сетевого HP-статуса), поэтому его никто