Save/restore CTun, AGC, FM step per XVTR slot; add FM step to web

- Add LastCTun, LastAGCMode, LastAGCTop to TXvtrEntry; SaveCurrentBand
  now captures all three in the XVTR branch; ActivateXvtrBand restores
  them on slot switch/startup (previously CTun was always reset to False
  and AGC was never saved/restored for XVTR)
- WebServer: expose fmstep_idx in state JSON so web clients sync the
  FM step from desktop state
- WebPageHtml: swap stepSel options to FM steps (6.25k/12.5k/20k/25k)
  when mode=FM, restore HF steps when leaving FM; syncs fmstep_idx
  from server on connect and mode change

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

WebServer.pas

@@ -212,6 +212,7 @@ type
     FFilterIdx:   Integer;
     FVfoB:        Double;
     FActiveVfo:   Integer;   // 0=A, 1=B
+    FFMStepIdx:   Integer;
     FStateLock:   TCriticalSection;
 
     // ── Callbacks ──
@@ -304,6 +305,7 @@ type
 
     property WebClientActive: Boolean read FWebClientActive;
     property FreqMhzDigits: Integer read FFreqMhzDigits write FFreqMhzDigits;
+    property FMStepIdx: Integer read FFMStepIdx write FFMStepIdx;
 
     property OnFreq:   TWebCmdFreq   read FOnFreq   write FOnFreq;
     property OnMode:   TWebCmdMode   read FOnMode   write FOnMode;
@@ -425,8 +427,9 @@ begin
   FClientLock  := TCriticalSection.Create;
   FStateLock   := TCriticalSection.Create;
   // Начальные значения состояния
-  FFreq    := 14200000;
-  FMode    := 1;
+  FFreq      := 14200000;
+  FMode      := 1;
+  FFMStepIdx := 3;   // 25 kHz default
   FFilterBW:= 2700;
   FAGCMode := 1;
   FAGCTop  := 90;
@@ -1296,7 +1299,8 @@ begin
       '"nr_mode":%d,"nr":%s,"nb_mode":%d,"nb":%s,"snb":%s,"anf":%s,"connected":%s,' +
       '"transmitting":%s,"drive":%d,"attn_idx":%d,"tuning":%s,"dup":%s,' +
       '"fwd_w":%.1f,"swr":%.2f,"pa_max_power":%.0f,' +
-      '"xvtr_current":%d,"xvtr_bands":%s,"freq_mhz_digits":%d}',
+      '"xvtr_current":%d,"xvtr_bands":%s,"freq_mhz_digits":%d,' +
+      '"fmstep_idx":%d}',
       [FFreq, FVfoB, FActiveVfo,
        FMode, MODE_N[FMode mod 8],
        FFilterIdx, FFilterBW,
@@ -1321,7 +1325,8 @@ begin
        BoolToStr(FTuning,  'true', 'false'),
        BoolToStr(FDuplex, 'true', 'false'),
        FFwdW, FSWR, FPAMaxPower,
-       FCurrentXvtr, XvtrJson, FFreqMhzDigits
+       FCurrentXvtr, XvtrJson, FFreqMhzDigits,
+       FFMStepIdx
       ], FS);
   finally
     FStateLock.Leave;