Catch the feed list up when the page comes back into view (#168)

All Subscriptions said 1 unread when the server had none. The badge is the page's own sum of its
feed list, loaded once and patched only by events the server sends when a scan or a download
changes a feed. Reading an item, marking everything read or unsubscribing sends none, so another
device's page kept its old counts, and an iPhone stops the event stream while the app is in the
background, missing everything meanwhile; the reconnect did not catch up.

The page now takes the feed list and the open list again when it comes back into view and when the
stream reconnects after a drop. A browser test reads an item behind the page's back and checks the
badge follows once the page is shown again; it fails without this.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

CHANGELOG.md

@@ -18,6 +18,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Fixed
 
+- The unread counts catch up when you come back to the page: an item read on another device, or while the phone app was in the background, no longer stays counted as unread until a reload.
 - A feed set to download 0 of its newest items downloads all of them, the whole back catalogue, as the server's 0 does; it downloaded nothing.
 - The feed list loads faster: it counts the items and files of your own feeds, not of every feed on the server.
 - Downloading or deleting a file the server no longer has answers "not found" instead of a server error.