fix: clear Dock Recent Documents when purging task records

## Description Previously, “Purge Record” only cleared in-app/aria2 history but did not clear macOS’s system-level “Recent Documents,” so Dock still showed old downloads. ## Related Issues Fixed #1776 ### Checklist: * [x] Have you checked to ensure there aren't other open [Pull Requests](../../../pulls) for the same update/change? * [x] Have you linted your code locally prior to submission? * [x] Have you successfully ran app with your changes locally?