Add configurable VFO frequency range with GHz support

- Settings > Display: new "VFO Display" control to select max frequency
  range (999 MHz / 9.999 GHz / 99.999 GHz), persisted as freq_mhz_digits
- FreqDisplay: extend digit map [0..10] to support up to 11 digit positions;
  keyboard navigation adapts to MinMhzDigits dynamically
- MainForm/LayoutTopVfoBlock: VFO panel width scales automatically with
  selected digit count using dynamic text measurement
- Web VFO: fix broken HTML (class attr not closed before data-s — wheel and
  hover were completely non-functional); rewrite fmtVfo to use variable MHz
  digit count synced from server state; fix missing </span> for .vfo-hz
- WebServer: publish freq_mhz_digits in state JSON; updated from
  ApplyFreqMhzDigits so desktop and web stay in sync
- Fix Int32 overflow on frequencies above ~2.15 GHz: CATEngine.Pad V param
  Int64, FormatFreq/FormatFreqSV Mhz var Int64 (Mhz*1000000 overflowed)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Settings.pas

@@ -194,6 +194,8 @@ type
     DisplayFPS:        Integer;  // spectrum/waterfall timer fps (1..100)
     // --- Theme ---
     LightTheme:        Boolean;  // False = dark (default), True = light
+    // --- VFO display digits ---
+    FreqMhzDigits:     Integer;  // minimum MHz digit count: 3=999MHz, 4=9.999GHz, 5=99.999GHz
     // --- PA (Power Amplifier) settings ---
     PAMaxPower:        Double;   // максимальная выходная мощность, Вт (5..200)
     PABandCal:         array[0..CFG_BAND_COUNT-1] of Double; // калибровка на диапазон 38.8..100.0
@@ -346,6 +348,7 @@ begin
   G.ShowWaterfall    := True;
   G.DisplayDuplex    := False;
   G.DisplayFPS       := 60;
+  G.FreqMhzDigits    := 3;
   // CAT defaults
   for i := 0 to 3 do begin
     G.CATSerialEnabled[i]  := False;
@@ -557,6 +560,7 @@ begin
   G.DisplayDuplex := JB(GObj,'display_duplex',False);
   G.DisplayFPS    := JI(GObj,'display_fps',60);
   G.LightTheme    := JB(GObj,'light_theme',False);
+  G.FreqMhzDigits := EnsureRange(JI(GObj,'freq_mhz_digits',3), 3, 5);
   // PA settings
   G.PAMaxPower := JD(GObj,'pa_max_power',100.0);
   for i := 0 to CFG_BAND_COUNT-1 do
@@ -636,6 +640,7 @@ begin
   JW(O,'display_duplex',G.DisplayDuplex);
   JW(O,'display_fps',G.DisplayFPS);
   JW(O,'light_theme',G.LightTheme);
+  JW(O,'freq_mhz_digits',G.FreqMhzDigits);
   // PA settings
   JW(O,'pa_max_power',G.PAMaxPower);
   for i := 0 to CFG_BAND_COUNT-1 do