Keep a feed, an OPML or a Patreon creator out of All Subscriptions (#288)

A switch in the feed's settings, In All Subscriptions, on its
subscription as hide_from_all. All Subscriptions' list and count leave
out a feed hidden on its own or through the OPML it is in, and the page's
unread count does the same. Signals read every feed as before, and
Currently Listening, which is All Subscriptions' in-progress filter, keeps
an episode under way whatever the feed's setting.

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

crates/ipx/CHANGELOG.md

@@ -20,6 +20,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - `/metrics` counts Signals: items judged and fitting, calls to Jev by how they ended, the time they took and the tokens TypeSafe counted, time since the judge's last pass, and keys refused; a failed call to Jev shows as a failed trace (#270, #275).
 - An admin setting for how many days back a new Signal reads (#276).
 - A list's trace says which filter, sort and page it was asked for, and whether a search, so a slow list can be told from the others (#287).
+- A feed, an OPML subscription or a Patreon creator can be left out of All Subscriptions: `hide_from_all` on `PATCH /api/feeds/{id}` and in the feed list. Set on an OPML or creator it covers every show in it; Signals and Currently Listening still read them (#288).
 - `/metrics` breaks Signals' items, fits and TypeSafe tokens out by person and by whose key paid, so the server's bill can be split (#278).
 - An admin setting, Signals for everyone on the server's TypeSafe key, so the server pays for Jev instead of each person (#271).