Fix crash on startup: call OnLimitChanged after _chkScale is initialized

The manual OnLimitChanged(null, EventArgs.Empty) call in the constructor
was placed before _chkScale was created, causing a NullReferenceException
because the handler reads _chkScale.Checked. Moved the call to after both
_limitBar and _chkScale are created and wired.

MainForm.cs

@@ -182,7 +182,6 @@ public class MainForm : Form
             Value = 30
         };
         _limitBar.ValueChanged += OnLimitChanged;
-        OnLimitChanged(null, EventArgs.Empty);
         _chkScale = new CheckBox
         {
             Text = "Scale",
@@ -191,6 +190,7 @@ public class MainForm : Form
             Checked = false
         };
         _chkScale.CheckedChanged += OnLimitChanged;
+        OnLimitChanged(null, EventArgs.Empty);
 
         Controls.AddRange(new Control[] { _lblBle, _lblWs, _lblStrength, _lblDeviceName, _txtDeviceName, _btnConnect, _btnTest, _btnMusic, _btnStop, _lblTrack, _lblGaugeA, _gaugeA, _lblGaugeB, _gaugeB, _lblLimit, _limitBar, _chkScale });