Adjustable Active Window Border Thickness

### Description of the new feature / enhancement

On large monitors or ultrawide displays it can sometimes be difficult to quickly identify which window is currently active, especially when switching windows using the keyboard (Alt+Tab or other shortcuts) rather than the mouse.

Windows only shows a very thin accent-colored border around the active window, which can be hard to notice.

Proposed solution

Add an optional PowerToys feature that highlights the active window with a configurable border.

Possible settings:
- Border thickness (e.g., 2–10 px)
- Custom color
- Optional glow or outline effect
- Enable/disable toggle

### Scenario when this would be used?

Users working on large or multi-monitor setups frequently switch between windows using the keyboard. A thicker colored border around the active window would make it immediately obvious which window currently has focus.

This would improve usability and accessibility, especially on high-resolution displays.

Notes

PowerToys already draws borders for features like "Always On Top". A similar visual indicator for the currently active window could reuse a similar approach.

### Supporting information

_No response_

Start by examining PowerToys' existing Always On Top border implementation, which the issue identifies as a similar visual indicator. Define how active-window detection, configurable thickness and color, optional effects, and enable/disable settings should work; the feature is done when the border reliably highlights the focused window across the described monitor setups.

Written by the indexing model from the issue text.