feat: unify sample-rate presets across desktop + web UIs

Sample-rate (span) presets were duplicated in three places and none was
authoritative: HPSDR set hardcoded in the desktop overlay (SPAN_RATES),
Pluto set in backend caps, and a separate hardcoded list in the web JS.
The web showed HPSDR rates even on Pluto, and the web adapter silently
dropped any rate outside a hardcoded HPSDR whitelist (so Pluto-only rates
like 960k/2304k never switched).

Single source of truth = backend caps -> controller:
- HPSDRNetwork.Caps now fills RatePresets [48k..1536k] (was nil).
- RadioBackend: named type TBackendRateArray.
- TRadioController.SampleRatePresets returns BackendCaps.RatePresets.

Both UIs derive from it:
- Desktop: ApplyBackendCapsToUI always feeds the overlay from
  SampleRatePresets (overlay no longer owns the HPSDR list).
- Web: WebServer.SetRatePresets + rate_presets in state JSON; hosts
  (daemon OnState/startup, GUI ApplyBackendCapsToUI/startup) push
  SampleRatePresets; JS builds span buttons dynamically from it.
- WebAdapter.SyncSpan validates against SampleRatePresets instead of a
  hardcoded whitelist, so any backend rate is accepted.

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

WebServer.pas

@@ -297,6 +297,7 @@ type
     FFreqMhzDigits:  Integer;     // 3=999MHz, 4=9.999GHz, 5=99.999GHz
     FXvtrBands:   TWebXvtrArray;  // список enabled XVTR (для web-UI)
     FDevices:     TWebDeviceArray; // saved+discovered устройства (для web-overlay)
+    FRatePresets: array of Integer; // sample-rate пресеты текущего бэкенда (для span-кнопок)
     FCurrentXvtr: Integer;        // -1 = HF, иначе индекс активного XVTR
     FOnXvtrBand:  TWebCmdXvtrBand;
 
@@ -392,6 +393,7 @@ type
     property OnXvtrBand: TWebCmdXvtrBand read FOnXvtrBand write FOnXvtrBand;
     procedure SetXvtrBands(const ABands: TWebXvtrArray; ACurrent: Integer);
     procedure SetDeviceList(const ADevices: TWebDeviceArray);
+    procedure SetRatePresets(const ARates: array of Integer);
     property OnSpan:   TWebCmdSpan   read FOnSpan   write FOnSpan;
     property OnVolume: TWebCmdVolume read FOnVolume write FOnVolume;
     property OnWfAGC:  TWebCmdWfAGC  read FOnWfAGC  write FOnWfAGC;
@@ -535,6 +537,8 @@ begin
   FCurrentXvtr  := -1;
   FFreqMhzDigits := 3;
   SetLength(FXvtrBands, 0);
+  // Bootstrap-набор рейтов (до connect): хост перезапишет под бэкенд (HPSDR/Pluto).
+  SetRatePresets([48000, 96000, 192000, 384000, 768000, 1536000]);
 end;
 
 procedure TWebServer.SetXvtrBands(const ABands: TWebXvtrArray; ACurrent: Integer);
@@ -564,6 +568,21 @@ begin
   end;
 end;
 
+procedure TWebServer.SetRatePresets(const ARates: array of Integer);
+// Список пресетов sample-rate текущего бэкенда (из TRadioController). Web строит
+// span-кнопки из него — HPSDR и Pluto имеют разные наборы.
+var i: Integer;
+begin
+  FStateLock.Enter;
+  try
+    SetLength(FRatePresets, Length(ARates));
+    for i := 0 to High(ARates) do
+      FRatePresets[i] := ARates[i];
+  finally
+    FStateLock.Leave;
+  end;
+end;
+
 destructor TWebServer.Destroy;
 begin
   Stop;
@@ -1542,13 +1561,21 @@ const
     ('LSB','USB','DSB','CWL','CWU','FM','AM','SAM');
 var
   FS: TFormatSettings;
-  XvtrJson, DevJson: string;
+  XvtrJson, DevJson, RateJson: string;
   i: Integer;
 begin
   FS := DefaultFormatSettings;
   FS.DecimalSeparator := '.';
   FStateLock.Enter;
   try
+    // Сборка массива rate_presets: [48000,96000,...] (span-кнопки web).
+    RateJson := '[';
+    for i := 0 to High(FRatePresets) do
+    begin
+      if i > 0 then RateJson := RateJson + ',';
+      RateJson := RateJson + IntToStr(FRatePresets[i]);
+    end;
+    RateJson := RateJson + ']';
     // Сборка массива xvtr_bands: [{"idx":0,"name":"2m"},...]
     XvtrJson := '[';
     for i := 0 to High(FXvtrBands) do
@@ -1586,7 +1613,7 @@ begin
 	      '"status_text":"%s","board_text":"%s","ip_text":"%s","supply_text":"%s",' +
 	      '"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}',
+	      '"fmstep_idx":%d,"devices":%s,"rate_presets":%s}',
       [FFreq, FVfoB, FActiveVfo,
        FMode, MODE_N[FMode mod 8],
        FFilterIdx, FFilterBW,
@@ -1615,7 +1642,7 @@ begin
 	       JsonEscape(FSupplyText), JsonEscape(FPLLText), JsonEscape(FRXText),
 	       JsonEscape(FTXText), JsonEscape(FSeqText),
 	       FCurrentXvtr, XvtrJson, FFreqMhzDigits,
-       FFMStepIdx, DevJson
+       FFMStepIdx, DevJson, RateJson
       ], FS);
   finally
     FStateLock.Leave;