Automatically recommend sites to archive

As described in the original concept for this extension:

>If the extension notices a user browsing a certain domain often, it will ask them if they'd like to archive it or not. If they choose yes, then it'll retroactively archive the history (going back some amount of days; not forever) and any future visit to that domain

Start with the original concept linked in the issue body and inspect the extension's existing browsing-history and ArchiveBox integration entry points. The issue does not name files, tests, or an implementation scope, so clarify the prompting, retention period, domain detection, and archival behavior before coding; done should include agreed behavior and tests for the full flow.

Written by the indexing model from the issue text.