v0.4.1: live updates also refresh the source sidebar

Extends v0.4.0 without a second request: the sidebar is updated client-side
from the rows the existing /feed/updates poll already returns.

- Each new row's data-source drives the sidebar: per-source + "All sources"
  unread counts bump; a first-time source is inserted into the list
  (alphabetically). Reuses the existing count-badge pattern.
- sourceLinks is now live-queried (was cached at load) so sources added live
  stay keyboard-navigable.
- No endpoint/model change. 142 tests pass; feed renders.

Caveat: while filtered to a single source, other new sources appear only on
reload (the poll is scoped to the selected view).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

CHANGELOG.md

@@ -9,6 +9,16 @@ former name, "Daybook".)
 
 _Nothing yet._
 
+## [0.4.1] — 2026-09-05
+
+### Changed
+- Live feed updates now also keep the **source sidebar** current: as new posts
+  arrive, per-source and total unread counts bump, and a source posting for the
+  first time is added to the list (alphabetically) — all derived client-side
+  from the polled rows, no extra request. Sources added live stay
+  keyboard-navigable. Caveat: while filtered to a single source, *other* new
+  sources still only appear on reload (the poll is scoped to the selected view).
+
 ## [0.4.0] — 2026-09-04
 
 ### Added
@@ -155,7 +165,8 @@ First tagged release.
 - Dockerised (Gunicorn + whitenoise), SQLite, `git`-based deploy with a
   runbook (`deploy/cloud_agent_deploy.md`) and health check.
 
-[Unreleased]: https://git.cygnus.systems/peter/daybook/compare/v0.4.0...HEAD
+[Unreleased]: https://git.cygnus.systems/peter/daybook/compare/v0.4.1...HEAD
+[0.4.1]: https://git.cygnus.systems/peter/daybook/compare/v0.4.0...v0.4.1
 [0.4.0]: https://git.cygnus.systems/peter/daybook/compare/v0.3.2...v0.4.0
 [0.3.2]: https://git.cygnus.systems/peter/daybook/compare/v0.3.1...v0.3.2
 [0.3.1]: https://git.cygnus.systems/peter/daybook/compare/v0.3.0...v0.3.1