Verify Views files against decompiled, extract embedded types

Fixed files:
- SkiaImageButton.cs: Added SVG support with multi-path search
- SkiaNavigationPage.cs: Added LinuxApplication.IsGtkMode check
- SkiaRefreshView.cs: Added ICommand support (Command, CommandParameter)
- SkiaTemplatedView.cs: Added missing using statements

Extracted embedded types to separate files (matching decompiled pattern):
- From SkiaMenuBar.cs: MenuBarItem, MenuItem, SkiaMenuFlyout, MenuItemClickedEventArgs
- From SkiaNavigationPage.cs: NavigationEventArgs
- From SkiaTabbedPage.cs: TabItem
- From SkiaVisualStateManager.cs: SkiaVisualStateGroupList, SkiaVisualStateGroup, SkiaVisualState, SkiaVisualStateSetter
- From SkiaSwipeView.cs: SwipeItem, SwipeStartedEventArgs, SwipeEndedEventArgs
- From SkiaFlyoutPage.cs: FlyoutLayoutBehavior (already separate)
- From SkiaIndicatorView.cs: IndicatorShape (already separate)
- From SkiaBorder.cs: SkiaFrame
- From SkiaCarouselView.cs: PositionChangedEventArgs
- From SkiaCollectionView.cs: SkiaSelectionMode, ItemsLayoutOrientation
- From SkiaContentPresenter.cs: LayoutAlignment

Verified matching decompiled:
- SkiaContextMenu.cs, SkiaFlexLayout.cs, SkiaGraphicsView.cs

Build: 0 errors

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Services/SystemThemeService.cs

@@ -425,57 +425,3 @@ public class SystemThemeService
         }
     }
 }
-
-/// <summary>
-/// System theme (light or dark mode).
-/// </summary>
-public enum SystemTheme
-{
-    Light,
-    Dark
-}
-
-/// <summary>
-/// Detected desktop environment.
-/// </summary>
-public enum DesktopEnvironment
-{
-    Unknown,
-    GNOME,
-    KDE,
-    XFCE,
-    MATE,
-    Cinnamon,
-    LXQt,
-    LXDE
-}
-
-/// <summary>
-/// Event args for theme changes.
-/// </summary>
-public class ThemeChangedEventArgs : EventArgs
-{
-    public SystemTheme NewTheme { get; }
-
-    public ThemeChangedEventArgs(SystemTheme newTheme)
-    {
-        NewTheme = newTheme;
-    }
-}
-
-/// <summary>
-/// System colors based on the current theme.
-/// </summary>
-public class SystemColors
-{
-    public SKColor Background { get; init; }
-    public SKColor Surface { get; init; }
-    public SKColor Primary { get; init; }
-    public SKColor OnPrimary { get; init; }
-    public SKColor Text { get; init; }
-    public SKColor TextSecondary { get; init; }
-    public SKColor Border { get; init; }
-    public SKColor Divider { get; init; }
-    public SKColor Error { get; init; }
-    public SKColor Success { get; init; }
-}