Add FM mode improvements: NFM/FM filters, CTCSS, squelch; ADC and web settings

FM modulation:
- Replace 10 generic FM filter buttons with NFM (2.5kHz dev/11kHz BW) and FM
  (5.0kHz dev/16kHz BW); deviation applied to both RX and TX via WDSP
- Add FM squelch panel (SQL toggle + slider 0..100, per-band save/restore)
  with WDSP SetRXAFMSQRun/SetRXAFMSQThreshold (threshold = level/200.0)
- Add CTCSS panel with on/off toggle and custom flat-button tone picker popup
  (38 standard tones 67.0..250.3 Hz, default 67.0); tone selection and enable
  state saved per band via SetTXACTCSS*
- FM panels (SQL, CTCSS) shown only in FM mode, layout via RelayoutBelowBands
- PanelFilter height shrinks in FM mode so panels sit tight below filters
- FlatButton: handle CMTextChanged to invalidate on Caption change

ADC settings (Dither/Random):
- Add DitherEnabled/RandomEnabled to TGlobalSettings (default true)
- Pass as bitmask to ConfigureDDCs DDC Specific packet bytes 5/6
- Exposed in Settings → Advanced tab with live apply via ApplyADCSettings

Web server settings:
- Add TWebSettings (enabled, port, bind_addr, user, pass) stored globally
- WebServer: configurable port/bind IP via ParseIPv4; Reconfigure method
- Exposed in Settings → Advanced tab with live apply via ApplyWebSettings

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

FlatButton.pas

@@ -8,7 +8,7 @@ unit FlatButton;
 interface
 
 uses
-  Classes, SysUtils, Controls, Graphics, LCLType, Types;
+  Classes, SysUtils, Controls, Graphics, LCLType, LMessages, Types;
 
 type
   TFlatButton = class(TGraphicControl)
@@ -27,6 +27,7 @@ type
     procedure Paint; override;
     procedure MouseEnter; override;
     procedure MouseLeave; override;
+    procedure CMTextChanged(var Msg: TLMessage); message CM_TEXTCHANGED;
     procedure MouseDown(Button: TMouseButton; Shift: TShiftState;
                         X, Y: Integer); override;
     procedure MouseUp(Button: TMouseButton; Shift: TShiftState;
@@ -131,6 +132,11 @@ begin
   Invalidate;
 end;
 
+procedure TFlatButton.CMTextChanged(var Msg: TLMessage);
+begin
+  Invalidate;
+end;
+
 procedure TFlatButton.MouseDown(Button: TMouseButton; Shift: TShiftState;
   X, Y: Integer);
 begin