feat: unify band plan across desktop + web UIs

Web band selector was hardcoded to the HF plan, so on Pluto it showed
160m..6m instead of the VHF/UHF plan and highlighted the wrong entry
(band switching itself already worked: web sends idx, controller maps it
via the IsPluto plan). Mirror the sample-rate unification.

Single source of truth = BoardUtils -> controller:
- BoardUtils: TBandInfo/TBandPlanArray + BuildBandPlan(Pluto).
- TRadioController.BandPlan returns BuildBandPlan(IsPluto).

Both UIs derive from it:
- Desktop already plan-aware (RelabelBands + RestoreBand) - unchanged.
- Web: WebServer.SetBands + "bands" in state JSON; hosts push
  BandPlan on connect/startup; JS builds the band selector from
  state.bands (BAND_N/BAND_F now dynamic).

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

MainForm.pas

@@ -479,6 +479,7 @@ type
     procedure OnXvtrSettingsChange(const X: TXvtrSettings);
     procedure PushXvtrToWeb;
     procedure PushRatePresetsToWeb;   // backend sample-rate пресеты → web
+    procedure PushBandsToWeb;         // backend band-план → web
     // XVTR helpers
     function  FindXvtrIdxForFreq(FreqHz: Double): Integer;
     function  XvtrTranslate(VisibleHz: Double): Double;
@@ -884,6 +885,7 @@ begin
   PushXvtrToWeb;
   PushDeviceListToWeb;   // saved-устройства сразу видны web-overlay
   PushRatePresetsToWeb;  // дефолтный бэкенд до connect; перезапишется на смене
+  PushBandsToWeb;
   FillChar(FCATLastGlobal, SizeOf(FCATLastGlobal), 0);
   FCATLastGlobal.CATTcpPort := 19090;
   for i := 0 to 3 do
@@ -3685,6 +3687,7 @@ begin
     FSampleRateOverlay.SetCurrentRate(FController.FSampleRate);
   end;
   PushRatePresetsToWeb;   // тот же источник зеркалим в web-морду
+  PushBandsToWeb;         // band-план бэкенда → web (HF ↔ VHF/UHF)
 
   // Отдельный Pluto RF-AGC блок под AGC: показываем и сдвигаем панели ниже.
   LayoutLeftPanel(Caps.HasHWGain);
@@ -5375,6 +5378,27 @@ begin
   FWebServer.SetRatePresets(FController.SampleRatePresets);
 end;
 
+procedure TMainForm.PushBandsToWeb;
+// Band-план бэкенда → web (HF / VHF-UHF). Единый источник — FController.BandPlan,
+// тот же BoardUtils-план, что и для desktop-кнопок (RelabelBands).
+var
+  Plan: TBandPlanArray;
+  Names: array of string;
+  Freqs: array of Double;
+  i: Integer;
+begin
+  if FWebServer = nil then Exit;
+  Plan := FController.BandPlan;
+  SetLength(Names, Length(Plan));
+  SetLength(Freqs, Length(Plan));
+  for i := 0 to High(Plan) do
+  begin
+    Names[i] := Plan[i].Name;
+    Freqs[i] := Plan[i].FreqHz;
+  end;
+  FWebServer.SetBands(Names, Freqs);
+end;
+
 procedure TMainForm.PushXvtrToWeb;
 var
   Arr: TWebXvtrArray;