Spot a call locally and wipe when the radio moves far on a QSY

With a call in the entry window, a move of more than 2 kHz on the same
band puts the call on the bandmap where it was heard and wipes the boxes,
as N1MM does. The spot goes to the other stations as ADDSPOT and to the
Spots broadcast, never to the cluster. ADDSPOT from other stations is
added to the bandmap.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

src/Nonemm.App/Configuration/Settings.cs

@@ -91,6 +91,11 @@ public sealed record Settings
 
     public int DigitalTuningToleranceHertz { get; init; } = 300;
 
+    /// How far the radio has to move on the band, in hertz, with a callsign
+    /// left in the entry window, before the call is spotted locally and the
+    /// boxes are wiped. N1MM uses 2 kHz.
+    public int QsySpotHertz { get; init; } = 2000;
+
     public int TuningToleranceFor(ModeCategory mode) => mode switch
     {
         ModeCategory.Phone => PhoneTuningToleranceHertz,