[ZoomIt] Add a laser pen with automatically fading ink

### Description of the new feature / enhancement

Add a laser pen tool that creates temporary annotations which automatically disappear after a short period.

### Scenario when this would be used?

Users often need to briefly highlight content during presentations, teaching sessions, PDF reviews, training, demonstrations, and screen sharing without leaving permanent drawings on the screen.

### Supporting information

Similar functionality exists in presentation and annotation tools where laser trails fade automatically after a few seconds. This provides a cleaner experience by drawing attention to content temporarily and reducing the need for manual cleanup of annotations.

The issue names no files, tests, or entry points. Start by locating ZoomIt's annotation implementation and existing drawing behavior, then determine how a laser annotation should be triggered and timed; done means the temporary ink fades automatically after a short period without requiring manual cleanup.

Written by the indexing model from the issue text.