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/components/Header.tsx

@@ -1,6 +1,7 @@
 "use client";
 import React, { useState, useEffect, useRef } from "react";
 import Link from "next/link";
+import { useRouter } from "next/navigation";
 import AppImage from "@/components/ui/AppImage";
 import {
   LinkedInIcon,
@@ -68,10 +69,18 @@ const navLinks: NavItem[] = [
 ];
 
 export default function Header() {
+  const router = useRouter();
   const [scrolled, setScrolled] = useState(false);
   const [mobileOpen, setMobileOpen] = useState(false);
   const [searchQuery, setSearchQuery] = useState("");
   const [searchFocused, setSearchFocused] = useState(false);
+
+  const submitSearch = () => {
+    const q = searchQuery.trim();
+    if (!q) return;
+    setMobileOpen(false);
+    router.push(`/search?q=${encodeURIComponent(q)}`);
+  };
   const [currentUserId, setCurrentUserId] = useState<string | null>(null);
   const [currentUserEmail, setCurrentUserEmail] = useState<string | null>(null);
   const [isAdmin, setIsAdmin] = useState(false);
@@ -440,6 +449,12 @@ export default function Header() {
                     onChange={(e) => setSearchQuery(e?.target?.value)}
                     onFocus={() => setSearchFocused(true)}
                     onBlur={() => setSearchFocused(false)}
+                    onKeyDown={(e) => {
+                      if (e.key === "Enter") {
+                        e.preventDefault();
+                        submitSearch();
+                      }
+                    }}
                     className="search-input search-input-enhanced pr-16"
                     aria-label="Search articles (press / to focus)"
                   />
@@ -456,18 +471,24 @@ export default function Header() {
                     <span className="search-kbd-hint" aria-hidden="true">/</span>
                   )}
                   {(searchQuery || searchFocused) && (
-                    <SearchIcon
-                      size={13}
-                      strokeWidth={1.75}
-                      className="absolute right-2.5 top-1/2 -translate-y-1/2 text-[#3b82f6] pointer-events-none transition-colors"
-                    />
+                    <button
+                      type="button"
+                      onClick={submitSearch}
+                      aria-label="Submit search"
+                      className="absolute right-2.5 top-1/2 -translate-y-1/2 text-[#3b82f6] hover:text-[#60a5fa] transition-colors cursor-pointer"
+                    >
+                      <SearchIcon size={13} strokeWidth={1.75} />
+                    </button>
                   )}
                   {!searchQuery && !searchFocused && (
-                    <SearchIcon
-                      size={13}
-                      strokeWidth={1.75}
-                      className="absolute right-8 top-1/2 -translate-y-1/2 text-[#666] pointer-events-none"
-                    />
+                    <button
+                      type="button"
+                      onClick={() => searchRef.current?.focus()}
+                      aria-label="Focus search"
+                      className="absolute right-8 top-1/2 -translate-y-1/2 text-[#666] hover:text-[#3b82f6] transition-colors cursor-pointer"
+                    >
+                      <SearchIcon size={13} strokeWidth={1.75} />
+                    </button>
                   )}
                 </div>
               </div>
@@ -585,14 +606,25 @@ export default function Header() {
                     <input
                       type="search"
                       placeholder="Search articles..."
+                      value={searchQuery}
+                      onChange={(e) => setSearchQuery(e?.target?.value)}
+                      onKeyDown={(e) => {
+                        if (e.key === "Enter") {
+                          e.preventDefault();
+                          submitSearch();
+                        }
+                      }}
                       className="search-input search-input-enhanced w-full pr-8"
                       aria-label="Search articles mobile"
                     />
-                    <SearchIcon
-                      size={13}
-                      strokeWidth={1.75}
-                      className="absolute right-2.5 top-1/2 -translate-y-1/2 text-[#666] pointer-events-none"
-                    />
+                    <button
+                      type="button"
+                      onClick={submitSearch}
+                      aria-label="Submit search"
+                      className="absolute right-2.5 top-1/2 -translate-y-1/2 text-[#666] hover:text-[#3b82f6] transition-colors cursor-pointer"
+                    >
+                      <SearchIcon size={13} strokeWidth={1.75} />
+                    </button>
                   </div>
                 </div>
               </div>