Feature request: bulk re-fetch

I'm migrating from Pocket, and a useful feature would be a bulk process that allows re-fetching all the links Wallabag couldn't fetch automatically, while keeping the original add date.

Start by tracing how the browser extension records links that Wallabag could not fetch and how it sends re-fetch requests. Define the bulk operation around those existing entry points, preserving each link's original add date, and verify that all previously failed links can be retried successfully.

Written by the indexing model from the issue text.