news relaunch step 1: extract the feed into NewsFeed.svelte, mount at / and /news

Pure refactor, no visible/behavioral change. The ~1065-line feed moves verbatim
from routes/+page.svelte into lib/components/NewsFeed.svelte; both routes/+page
and the new routes/news render it. Link generation is base-aware (feedBase()):
on `/` it builds `/?…` exactly as today (bug-for-bug parity); on `/news` it
builds `/news?…` so /news is self-coherent. At cutover, `/` becomes the hub and
the feed lives only at /news.

/news is kept hidden during the transition (noindex, follow) so we never publish
a duplicate indexable feed: route <meta robots> + a Caddy @newsHidden X-Robots-Tag
(follow, so link equity flows). Removed at cutover, when /news enters the sitemap.

27/27 frontend tests green; build clean; /news.html prerenders.

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

frontend/src/routes/news/+page.svelte

@@ -0,0 +1,12 @@
+<script>
+  // /news — the feed's permanent home. During transition it renders the SAME extracted
+  // NewsFeed as `/` and stays hidden (noindex) so we never publish a duplicate indexable
+  // surface. At cutover the noindex is dropped and /news enters the sitemap.
+  import NewsFeed from '$lib/components/NewsFeed.svelte';
+</script>
+
+<svelte:head>
+  <meta name="robots" content="noindex, follow" />
+</svelte:head>
+
+<NewsFeed />