Add keyboard focus visual indicator for ToggleSwitch control.

[c3n9]

Problem
The ToggleSwitch control in Material.Avalonia lacks proper visual feedback when focused via keyboard navigation (Tab, Shift+Tab), gamepad, or other input methods. This creates accessibility issues and poor user experience for:

• Users who rely on keyboard navigation exclusively
• Accessibility requirements (WCAG 2.1 success criterion 2.4.7)
• Gamepad and TV interface scenarios
• Power users preferring keyboard shortcuts

Technical Changes

• Added focus state handling in ToggleSwitch template
• Extended ripple effect system to support focus state
• Disabled default focus adorner in favor of Material Design visuals
• Added smooth transitions for focus state changes

[c3n9]

If it's a good idea, I or someone else can continue adding effects to all the elements. To completely remove the ugly dot focus limiter. It doesn't fit into the overall visual picture in any way.

[c3n9]

before

after

[SKProCH]

Overall fine

[c3n9]

The FocusAdorner property is used to show a default focus visual, typically a Border, around a Control with :focus-visible. When using :focus-visible to show a custom visual indicator, setting FocusAdorner to null will avoid showing a duplicate indicator.

[c3n9]

I changed focus to focus-visible.

[c3n9]

Now the visual effect will only work when navigating with the keyboard. This will allow us to improve all other controls in the future.