/api/status, for Homepage's dashboard (#67)

The iPX tile on Homepage was a bare link: nothing in ipx gave a summary a
customapi widget could read. /api/status serves what `ipx status` prints
(feeds, items pending, files downloaded), from the same function the
control socket answers with, plus the version. It sits behind sign-in
like the rest of /api; Homepage sends the shared [web] token as the
ipx_token cookie.

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

CHANGELOG.md

@@ -7,6 +7,11 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Added
+
+- `/api/status` gives the number of feeds, items waiting to download and files downloaded, and
+  the version, for a dashboard such as Homepage.
+
 ### Changed
 
 - The Modern theme takes its colours from the new logo: its navy, the blue of its bars and the