fix: prevent multiple subscriptions to Loaded event

Co-authored-by: Copilot <[email protected]>

Author: Illustar0

components/RangeSelector/src/RangeSelector.cs

@@ -149,6 +149,7 @@ protected override void OnApplyTemplate()
         tb.Measure(new Size(double.PositiveInfinity, double.PositiveInfinity));
 
         // Ensure thumbs and active rectangle are synced after the control is fully loaded
+        Loaded -= RangeSelector_Loaded;
         Loaded += RangeSelector_Loaded;
 
         base.OnApplyTemplate();