Fix article-view swipe being swallowed by Chrome-on-Android back gesture

On real Android touchscreens, a horizontal drag on content with nothing
left to scroll horizontally gets claimed by Chrome's native
swipe-to-go-back/forward gesture before our own touchend listener
(article-view swipe navigation) ever sees it — silently, with no
touchend firing at all. Synthetic touch testing (mouse-drag emulation
in devtools) doesn't go through that gesture recognizer, so it worked
there while doing nothing on an actual phone.

Fix: overscroll-behavior-x: contain on body stops Chrome from claiming
the gesture for its own navigation, letting our touchend fire normally.

Also drops the overflow-x: hidden added to .article-single for the
slide transition — body already has it (for the same full-bleed-image
reason), so it was redundant.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

vue/src/components/RssFeeds.vue

@@ -367,7 +367,6 @@ onMounted(async () => {
   align-items: center;
   padding-top: 1em;
   padding-bottom: 5rem;
-  overflow-x: hidden;
 }
 
 .article-feature {