feat: QO-100 beacon lock — robustness, persistence, FT8-aware UI

Builds on the beacon-lock baseline: keeps the proven display-FFT control
path (hardware-LO trim folded into the active transverter LOError), and
hardens it. The narrowband NCO/FLL scaffold (BeaconLock.pas) is removed —
it was never in the control path.

- RadioController:
  * Persist live: each correction folds straight into the active xvtr
    LOError (visible in Settings, survives restart as LNB calibration);
    disk writes throttled. FBeaconLockHz is now only a session indicator.
  * Robust tracking vs nearby signals: narrow ±2 kHz gate while locked
    (±6 kHz only for acquisition), slew-rate outlier rejection (a sudden
    centroid jump = interferer, not slow LNB drift → ignored), and lobe
    shape validation in MeasureBeaconFFT (width + power symmetry) so a CW
    carrier / one-sided neighbour isn't mistaken for the BPSK beacon.
    Prominence measured over the in-window noise floor (gate-width robust).
  * Fast convergence: feed-forward (predict post-retune position so the
    window follows the beacon through the jump) + near-deadbeat correction
    on the manual click → one click locks instead of repeated tapping.
  * Single central BPSK beacon (10489.750); dead CoarseBeaconOffset and
    unused throttle counters removed; stale NCO/FLL/4 Hz comments fixed.
- WDSPEngine: drop the per-sample TBeaconTracker RX-IQ tap (tracker gone).
- MainForm: BEACON is now a plain button, shown only on Pluto in a
  transverter. Lock status (off / click / search / LOCK + correction +
  prominence) moves to status-bar field 7 in place of PLL on Pluto;
  openHPSDR keeps PLL there.
- SettingsForm/StatusBar: widen LO Error field to ±10 MHz (QO-100 LNBs
  drift hundreds of kHz) and widen status field 7 for the beacon text.

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

SettingsForm.pas

@@ -3211,7 +3211,9 @@ begin
       FXvtrBegin[i] := MakeFlt(Grp, BEG_X,     Y, BEG_W,   0.0, 50000.0, 0.001, 3);
       FXvtrEnd[i]   := MakeFlt(Grp, END_X,     Y, END_W,   0.0, 50000.0, 0.001, 3);
       FXvtrLOOff[i] := MakeFlt(Grp, LO_X,      Y, LO_W, -50000.0, 50000.0, 0.001, 6);
-      FXvtrLOErr[i] := MakeFlt(Grp, ERR_X,     Y, ERR_W, -99999.0, 99999.0, 1.0, 0);
+      // диапазон ±10 МГц: QO-100 LNB без опоры легко уходит на сотни кГц, и
+      // beacon-lock складывает свою коррекцию сюда (живая калибровка LNB).
+      FXvtrLOErr[i] := MakeFlt(Grp, ERR_X,     Y, ERR_W, -9999999.0, 9999999.0, 1.0, 0);
       FXvtrRXGain[i]:= MakeFlt(Grp, GAIN_X,    Y, GAIN_W,  -60.0, 60.0, 0.1, 1);
       // Чекбокс RX Only центрируем
       FXvtrRXOnly[i]:= MakeChk(Grp, RXO_X + (RXO_W - 22) div 2,  Y + 2);