Always On Top - add default transparency when pinned always on top

### Description of the new feature / enhancement

Add the ability to set a default transparency when an app is made Always On Top.

### Scenario when this would be used?

Reduces manual setting of transparency level when it is a regular requirement.

### Supporting information

_No response_

No files, tests, or entry points are named. Start by locating the Always On Top utility and its existing pinning and transparency settings, then determine where the default can be configured. Done means a saved default transparency is applied when an app is pinned Always On Top, with coverage for the setting and behavior.

Written by the indexing model from the issue text.