Fix v0.1.18 startup crash: drift background via Canvas, not RenderTransform

MainWindow's moving background animated RenderTransform, for which Avalonia
registers no default animator — applying the style threw "No animator registered
for the property RenderTransform" and aborted startup before the window showed
(v0.1.18 crashed on launch for everyone). Drift the blobs by animating their
Canvas anchors instead (double has a built-in animator). Verified the app
launches and stays up.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: dooly123

src/BasisPM.App/Views/MainWindow.axaml

@@ -22,35 +22,37 @@
                     </Animation>
                 </Style.Animations>
             </Style>
+            <!-- Blobs drift by animating their Canvas anchors (double → built-in animator).
+                 RenderTransform has no default animator in Avalonia and throws at load. -->
             <Style Selector="Ellipse.blobA">
                 <Style.Animations>
                     <Animation Duration="0:0:23" IterationCount="INFINITE" PlaybackDirection="Alternate" Easing="SineEaseInOut">
-                        <KeyFrame Cue="0%"><Setter Property="RenderTransform" Value="translate(0px,0px)"/></KeyFrame>
-                        <KeyFrame Cue="100%"><Setter Property="RenderTransform" Value="translate(80px,60px)"/></KeyFrame>
+                        <KeyFrame Cue="0%"><Setter Property="Canvas.Left" Value="-60"/><Setter Property="Canvas.Top" Value="-40"/></KeyFrame>
+                        <KeyFrame Cue="100%"><Setter Property="Canvas.Left" Value="20"/><Setter Property="Canvas.Top" Value="30"/></KeyFrame>
                     </Animation>
                 </Style.Animations>
             </Style>
             <Style Selector="Ellipse.blobB">
                 <Style.Animations>
                     <Animation Duration="0:0:29" IterationCount="INFINITE" PlaybackDirection="Alternate" Easing="SineEaseInOut">
-                        <KeyFrame Cue="0%"><Setter Property="RenderTransform" Value="translate(0px,0px)"/></KeyFrame>
-                        <KeyFrame Cue="100%"><Setter Property="RenderTransform" Value="translate(-70px,50px)"/></KeyFrame>
+                        <KeyFrame Cue="0%"><Setter Property="Canvas.Right" Value="-80"/><Setter Property="Canvas.Top" Value="60"/></KeyFrame>
+                        <KeyFrame Cue="100%"><Setter Property="Canvas.Right" Value="-10"/><Setter Property="Canvas.Top" Value="115"/></KeyFrame>
                     </Animation>
                 </Style.Animations>
             </Style>
             <Style Selector="Ellipse.blobC">
                 <Style.Animations>
                     <Animation Duration="0:0:34" IterationCount="INFINITE" PlaybackDirection="Alternate" Easing="SineEaseInOut">
-                        <KeyFrame Cue="0%"><Setter Property="RenderTransform" Value="translate(0px,0px)"/></KeyFrame>
-                        <KeyFrame Cue="100%"><Setter Property="RenderTransform" Value="translate(-60px,-45px)"/></KeyFrame>
+                        <KeyFrame Cue="0%"><Setter Property="Canvas.Left" Value="280"/><Setter Property="Canvas.Bottom" Value="-40"/></KeyFrame>
+                        <KeyFrame Cue="100%"><Setter Property="Canvas.Left" Value="210"/><Setter Property="Canvas.Bottom" Value="20"/></KeyFrame>
                     </Animation>
                 </Style.Animations>
             </Style>
             <Style Selector="Ellipse.blobD">
                 <Style.Animations>
                     <Animation Duration="0:0:26" IterationCount="INFINITE" PlaybackDirection="Alternate" Easing="SineEaseInOut">
-                        <KeyFrame Cue="0%"><Setter Property="RenderTransform" Value="translate(0px,0px)"/></KeyFrame>
-                        <KeyFrame Cue="100%"><Setter Property="RenderTransform" Value="translate(55px,-40px)"/></KeyFrame>
+                        <KeyFrame Cue="0%"><Setter Property="Canvas.Right" Value="120"/><Setter Property="Canvas.Bottom" Value="-30"/></KeyFrame>
+                        <KeyFrame Cue="100%"><Setter Property="Canvas.Right" Value="55"/><Setter Property="Canvas.Bottom" Value="30"/></KeyFrame>
                     </Animation>
                 </Style.Animations>
             </Style>