Popular button in the sidebar; the popular list counts everyone

- A Popular button beside + Feed opens the popular list directly; the
  Add feed dialog keeps it too.
- The list counts every subscriber, you included. Your own feeds stay on
  it, marked Subscribed, and clicking one opens it. Private feeds and
  feeds inside an OPML are still never listed, for anyone.
- GET /api/popular rows carry `subscribed`.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016HdTEWQNrzyFULijigkmMn

CHANGELOG.md

@@ -10,6 +10,16 @@ The long form, with what was wrong before and how it was found, is in
 
 ## [Unreleased]
 
+### Added
+
+- A Popular button at the top of the feed list opens the popular list without going through
+  Add feed.
+
+### Changed
+
+- The popular list counts everyone, you included. Your own feeds stay on it, marked Subscribed,
+  and clicking one opens it.
+
 ## [0.3.0] - 2026-09-11
 
 ### Added