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>

RadioController.pas

@@ -547,6 +547,8 @@ type
     // Единый источник пресетов sample-rate для UI (desktop overlay + web).
     // Берётся из caps текущего бэкенда (HPSDR 48k..1536k / Pluto 576k..5760k).
     function  SampleRatePresets: TBackendRateArray;
+    // Единый источник band-плана для UI (HF / VHF-UHF по типу бэкенда).
+    function  BandPlan: TBandPlanArray;
     // True если активный бэкенд — Pluto (VHF/UHF band-план вместо HF).
     function  IsPluto: Boolean;
     // Человекочитаемое имя подключённой платы для статус-строки (UI/Web).
@@ -3162,6 +3164,11 @@ begin
   Result := BackendCaps.RatePresets;
 end;
 
+function TRadioController.BandPlan: TBandPlanArray;
+begin
+  Result := BuildBandPlan(IsPluto);
+end;
+
 function TRadioController.IsPluto: Boolean;
 begin
   Result := (FNetwork <> nil) and (FNetwork.Caps.Kind = bkPluto);