Update hover styles for hover buttons

src/PicView.Avalonia/Views/UC/Buttons/AltClose.axaml

@@ -13,7 +13,7 @@
     <Button
         Background="{DynamicResource AltBackgroundColor}"
         BorderThickness="1,0,0,1"
-        Classes="ButtonBorder noBorderHover"
+        Classes="ButtonBorder hover"
         ClickMode="Release"
         Command="{CompiledBinding ExitCommand}"
         CornerRadius="0,0,0,0"

src/PicView.Avalonia/Views/UC/Buttons/AltMinimize.axaml

@@ -14,7 +14,7 @@
         Background="{DynamicResource AltBackgroundColor}"
         BorderBrush="{DynamicResource MainBorderColor}"
         BorderThickness="1,0,0,0"
-        Classes="ButtonBorder noBorderHover"
+        Classes="ButtonBorder hover"
         ClickMode="Release"
         Command="{CompiledBinding MinimizeCommand}"
         CornerRadius="0,0,0,10"

src/PicView.Avalonia/Views/UC/Buttons/AltRestore.axaml

@@ -14,7 +14,7 @@
         Background="{DynamicResource AltBackgroundColor}"
         BorderBrush="{DynamicResource MainBorderColor}"
         BorderThickness="1,0,0,1"
-        Classes="ButtonBorder noBorderHover"
+        Classes="ButtonBorder hover"
         ClickMode="Release"
         Command="{CompiledBinding ToggleFullscreenCommand}"
         CornerRadius="0,0,0,0"