ZoomIt - Add default directory to save snips

### Description of the new feature / enhancement

Pressing Ctrl + Shift + 6 currently opens a dialog where we have to navigate to a directory and manually enter a file name to save the snip. Instead, there should be an option to predefine a directory so that whenever Ctrl + Shift + 6 is pressed, the snip is automatically saved to that location without prompting for a folder or file name.

### Scenario when this would be used?

This would be especially useful during live presentations or while explaining concepts on screen. In such situations, I often sketch or annotate things that I may want to revisit or share later. Having to pause and manually save each snip disrupts the flow and takes unnecessary time. Automatically saving captures to a predefined directory would make the process seamless and allow me to stay focused on presenting.

### Supporting information

_No response_

Start with the ZoomIt implementation for the Ctrl + Shift + 6 shortcut and trace how it currently opens the save dialog. Define how a user-selected default directory is configured and verify that pressing the shortcut saves the snip there without prompting for a folder or file name.

Written by the indexing model from the issue text.