Bug: Mark All as Read incorrectly affects news items fetched in background

[fish42]

When you "Mark All as Read", the web UI does not only mark as read items that are on the screen (and which the user knows about), but also fresh items that were fetched by the backend after the Feedbin page has been loaded (but which have never been been shown to the user). Thus, news items that have been posted while the user was busy reading will be silently marked as read, too, and the user will never see them in the UI.

This is clearly not what the user expects. Effectively, news entries can get lost this way, so this behavior should be fixed.

Reeder on iPhone does the right thing: "mark all as read" only considers the news items that where posted before the last sync. If the user refreshes/syncs again after mark all as read, later items are shown as new.

[Zegnat]

This is a duplicate of #156: "Mark all as read" marks unseen articles as "Read".