refactor(DrawerContainer): migrate Transitions from C# to XAML theme

- Removed ConfigureTransitions method and lifecycle hooks (OnLoaded/OnUnloaded)
- Added ^[IsMotionEnabled=True] style selector with SolidColorBrushTransition for Background property
- Transitions now handled declaratively in XAML theme

src/AtomUI.Desktop.Controls/Drawer/DrawerContainer.cs

@@ -1,5 +1,4 @@
 using System.Diagnostics;
-using AtomUI.Animations;
 using AtomUI.Controls;
 using AtomUI.Controls.Primitives;
 using AtomUI.Desktop.Controls.Themes;
@@ -12,7 +11,6 @@ using Avalonia.Controls.Primitives;
 using Avalonia.Controls.Templates;
 using Avalonia.Data;
 using Avalonia.Input;
-using Avalonia.Interactivity;
 using Avalonia.Layout;
 using Avalonia.Media;
 using Avalonia.Media.Transformation;
@@ -449,45 +447,4 @@ internal class DrawerContainer : ContentControl
             _infoContainer.RenderTransform = _originInfoContainerTransform;
         }
     }
-
-    protected override void OnPropertyChanged(AvaloniaPropertyChangedEventArgs change)
-    {
-        base.OnPropertyChanged(change);
-        if (IsLoaded)
-        {
-            if (change.Property == IsMotionEnabledProperty)
-            {
-                ConfigureTransitions(true);
-            }
-        }
-    }
-
-    private void ConfigureTransitions(bool force)
-    {
-        if (IsMotionEnabled)
-        {
-            if (force || Transitions == null)
-            {
-                Transitions = [
-                    TransitionUtils.CreateTransition<SolidColorBrushTransition>(Border.BackgroundProperty)
-                ];
-            }
-        }
-        else
-        {
-            Transitions = null;
-        }
-    }
-
-    protected override void OnLoaded(RoutedEventArgs e)
-    {
-        base.OnLoaded(e);
-        ConfigureTransitions(false);
-    }
-
-    protected override void OnUnloaded(RoutedEventArgs e)
-    {
-        base.OnUnloaded(e);
-        Transitions = null;
-    }
 }

src/AtomUI.Desktop.Controls/Drawer/Themes/DrawerContainerTheme.axaml

@@ -36,6 +36,14 @@
                 Value="{atom:SharedTokenResource MotionDurationSlow}" />
         <Setter Property="MaskBgColor"
                 Value="{atom:SharedTokenResource ColorBgMask}" />
-        
+
+        <Style Selector="^[IsMotionEnabled=True]">
+            <Setter Property="Transitions">
+                <Transitions>
+                    <atom:SolidColorBrushTransition Property="Background" Duration="{atom:SharedTokenResourceValue Kind=MotionDurationMid}" />
+                </Transitions>
+            </Setter>
+        </Style>
+
     </ControlTheme>
 </ResourceDictionary>