An OPML's page lists its shows' items together, not the shows (#283)

GET /api/feeds/{id}/entries for an OPML or a Patreon creator now lists the
items of the shows in it the person subscribes to, as All Subscriptions does
every feed's. The shows are looked up first and queried by list: an OR with a
subquery, or an IN over one, made a single feed's page a sequential scan of
entries (clarkesworld 10 ms to 26 ms or a second, EXPLAIN on production), so a
single feed keeps its `feed_id = $1`.

The page draws the OPML with its own header and the item list, tabs, search
and sort of any feed, with the feed column showing which show each is from.
A show's scan or change refreshes its OPML's list.

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

web/CHANGELOG.md

@@ -19,6 +19,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Changed
 
+- An OPML subscription's page lists the items of all its shows together, newest first, with the same tabs, search and sort as a show's, in place of a list of the shows; the shows are still in the folder in the feed list (#283).
 - Unless the server pays for them, Signals are turned on in Settings with your own TypeSafe key, and the Signals folder shows only once they are on (#271).
 - A Signal's dialog says how far back it reads, and that an edit reads again only what was picked out (#276).