feat: Implement AutoReverse support for Timeline animations and Storyboard containers

src/SamplesApp/UITests.Shared/UITests.Shared.projitems

@@ -5290,6 +5290,10 @@
       <SubType>Designer</SubType>
       <Generator>MSBuild:Compile</Generator>
     </Page>
+    <Page Include="$(MSBuildThisFileDirectory)Windows_UI_Xaml_Media_Animation\DoubleAnimation_AutoReverse.xaml">
+      <SubType>Designer</SubType>
+      <Generator>MSBuild:Compile</Generator>
+    </Page>
     <Page Include="$(MSBuildThisFileDirectory)Windows_UI_Xaml_Media_Animation\DoubleAnimation_RenderTransformOrigin.xaml">
       <SubType>Designer</SubType>
       <Generator>MSBuild:Compile</Generator>
@@ -8932,6 +8936,9 @@
     <Compile Include="$(MSBuildThisFileDirectory)Windows_UI_Xaml_Media_Animation\DoubleAnimation_Opacity_TextBlock.xaml.cs">
       <DependentUpon>DoubleAnimation_Opacity_TextBlock.xaml</DependentUpon>
     </Compile>
+    <Compile Include="$(MSBuildThisFileDirectory)Windows_UI_Xaml_Media_Animation\DoubleAnimation_AutoReverse.xaml.cs">
+      <DependentUpon>DoubleAnimation_AutoReverse.xaml</DependentUpon>
+    </Compile>
     <Compile Include="$(MSBuildThisFileDirectory)Windows_UI_Xaml_Media_Animation\DoubleAnimation_RenderTransformOrigin.xaml.cs">
       <DependentUpon>DoubleAnimation_RenderTransformOrigin.xaml</DependentUpon>
     </Compile>

src/SamplesApp/UITests.Shared/Windows_UI_Xaml_Media_Animation/DoubleAnimation_AutoReverse.xaml

@@ -0,0 +1,58 @@
+<UserControl
+	x:Class="GenericApp.Views.Content.UITests.Animations.DoubleAnimation_AutoReverse"
+	xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
+	xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+	xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
+	xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
+	mc:Ignorable="d"
+	d:DesignHeight="600"
+	d:DesignWidth="400">
+
+	<Grid>
+		<Grid.RowDefinitions>
+			<RowDefinition Height="Auto" />
+			<RowDefinition Height="Auto" />
+			<RowDefinition Height="*" />
+		</Grid.RowDefinitions>
+
+		<StackPanel Grid.Row="0" Orientation="Horizontal" Spacing="10" Margin="10">
+			<Button x:Name="StartButton" Content="Start" Click="StartAnimation" />
+			<Button x:Name="StopButton" Content="Stop" Click="StopAnimation" />
+		</StackPanel>
+
+		<TextBlock Grid.Row="1" x:Name="StatusText" Text="Click Start to begin animation" Margin="10" />
+
+		<Grid Grid.Row="2" Margin="20">
+			<Rectangle x:Name="AnimatedRectangle"
+				Width="50"
+				Height="50"
+				Fill="{ThemeResource SystemAccentColorBrush}"
+				HorizontalAlignment="Left"
+				VerticalAlignment="Top">
+				<Rectangle.RenderTransform>
+					<TranslateTransform x:Name="RectTransform" />
+				</Rectangle.RenderTransform>
+			</Rectangle>
+
+			<StackPanel VerticalAlignment="Bottom" Margin="10">
+				<TextBlock Text="AutoReverse=True" FontWeight="Bold" Margin="0,0,0,10" />
+				<TextBlock Text="Duration: 2 seconds" />
+				<TextBlock Text="From: 0, To: 300" />
+				<TextBlock Text="Expected: Move right, then back to start" TextWrapping="Wrap" />
+			</StackPanel>
+		</Grid>
+
+		<Grid.Resources>
+			<Storyboard x:Key="MoveStoryboard">
+				<DoubleAnimation
+					Storyboard.TargetName="RectTransform"
+					Storyboard.TargetProperty="X"
+					From="0"
+					To="300"
+					Duration="0:0:2"
+					AutoReverse="True"
+					FillBehavior="HoldEnd" />
+			</Storyboard>
+		</Grid.Resources>
+	</Grid>
+</UserControl>

src/SamplesApp/UITests.Shared/Windows_UI_Xaml_Media_Animation/DoubleAnimation_AutoReverse.xaml.cs

@@ -0,0 +1,42 @@
+using System;
+using Microsoft.UI.Xaml;
+using Microsoft.UI.Xaml.Controls;
+using Microsoft.UI.Xaml.Media.Animation;
+using Uno.UI.Samples.Controls;
+
+namespace GenericApp.Views.Content.UITests.Animations
+{
+	[Sample("Animations", Description = "Demonstrates AutoReverse functionality. The rectangle should move right then back to the start position.")]
+	public sealed partial class DoubleAnimation_AutoReverse : UserControl
+	{
+		private Storyboard _storyboard;
+
+		public DoubleAnimation_AutoReverse()
+		{
+			this.InitializeComponent();
+		}
+
+		private void StartAnimation(object sender, RoutedEventArgs e)
+		{
+			if (_storyboard == null)
+			{
+				_storyboard = (Storyboard)Resources["MoveStoryboard"];
+				_storyboard.Completed += OnStoryboardCompleted;
+			}
+
+			StatusText.Text = "Animation started...";
+			_storyboard.Begin();
+		}
+
+		private void StopAnimation(object sender, RoutedEventArgs e)
+		{
+			_storyboard?.Stop();
+			StatusText.Text = "Animation stopped";
+		}
+
+		private void OnStoryboardCompleted(object sender, object e)
+		{
+			StatusText.Text = "Animation completed - rectangle should be back at start position";
+		}
+	}
+}