P0-3/4/5: route error boundary, null guards, slug fallback, search

P0-3 (category page crash):
- Add src/app/error.tsx and src/app/global-error.tsx so any future render
  error shows a real ref id instead of the bare client-exception toast.
- NewsPageClient: null-guard every field accessed during search/category/
  sort filtering and article render (title, excerpt, author, tags,
  category, date, image, alt). The user-visible link
  /news?category=live-production now also hydrates filter state from
  ?category= and ?search= search-params, so the dropdown actually filters.

P0-4 (/articles/[slug] 404s):
- /articles/[slug] and /news/[slug]: on slug miss, redirect("/news")
  instead of notFound(). Dead links from the hardcoded NewsTicker /
  FeaturedBento / ArticleFeed arrays now land on the news index instead
  of dead-ending on 404.
- legacy-source: add searchLegacyArticles() (title/excerpt/author ilike).

P0-5 (header search):
- Header: wire Enter on the desktop and mobile search inputs and make
  both search icons clickable buttons. Submits to /search?q=<query>.
- New /search route: server component that runs searchLegacyArticles
  and renders results in the same card style as /news.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/lib/articles/legacy-source.ts

@@ -170,6 +170,28 @@ export async function getLegacyArticlesBySection(
   }
 }
 
+export async function searchLegacyArticles(
+  query: string,
+  limit = 50,
+): Promise<Article[]> {
+  const q = (query || "").trim();
+  if (!q) return [];
+  try {
+    const like = `%${q.replace(/[%_]/g, " ")}%`;
+    const { data, error } = await client()
+      .from("wp_imported_posts")
+      .select(SELECT_COLS)
+      .eq("status", "published")
+      .or(`title.ilike.${like},excerpt.ilike.${like},author_name.ilike.${like}`)
+      .order("wp_published_at", { ascending: false })
+      .limit(limit);
+    if (error || !data) return [];
+    return (data as ImportedPostRow[]).map((r) => rowToArticle(r, "news"));
+  } catch {
+    return [];
+  }
+}
+
 export async function getLegacyRecentSlugs(limit = 200): Promise<string[]> {
   try {
     const { data } = await client()