Keep a feed out of Signals, and a feed's settings in named parts (#289, #290)

hide_from_signals on a subscription, on an OPML or creator covering every
show in it, as hide_from_all does for All Subscriptions: the judge does
not put its items to Jev, and each Signal's list and counts leave them
out. shown_in() is the one SQL rule for both.

The settings dialog had grown one captioned setting at a time into a
single column, one part boxed and the rest not. It is in named parts now,
the name in a column beside the controls and above them on a phone, ruled
apart; All Subscriptions and Signals carry the sidebar's icons. The
address, the same for everyone, moves to the foot.

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

crates/ipx/CHANGELOG.md

@@ -21,6 +21,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - 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).
+- A feed, an OPML subscription or a Patreon creator can be kept out of Signals: `hide_from_signals` on `PATCH /api/feeds/{id}` and in the feed list. Jev is not asked about its items, so they cost nothing, and they are left out of each Signal's list and counts (#289).
 - `/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).