ads: add in-content 728x90 banner to gear, technology, forum, authors

These four landing pages already had the site-wide header leaderboard
via <Header />, but no additional in-content banner. Add one 728x90
slot at the bottom of the main column on each, gated on
ADS_728X90.length > 0 and hidden on mobile to match the header
banner's display rules.

  - /gear            — category landing
  - /technology      — category landing
  - /forum           — community landing
  - /authors/[slug]  — author profile

Brings these pages in line with /show-coverage and /about/* which got
the same treatment earlier.

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

src/app/technology/page.tsx

@@ -4,6 +4,8 @@ import Link from "next/link";
 import Header from "@/components/Header";
 import Footer from "@/components/Footer";
 import AppImage from "@/components/ui/AppImage";
+import AdImage from "@/components/AdImage";
+import { ADS_728X90, shuffle } from "@/lib/ads";
 import { getLegacyArticlesBySection } from "@/lib/articles/legacy-source";
 
 export const revalidate = 1800;
@@ -112,6 +114,13 @@ export default async function TechnologyPage() {
             </Link>
           ))}
         </div>
+
+        {/* In-content 728x90 banner */}
+        {ADS_728X90.length > 0 && (
+          <div className="mt-12 hidden md:flex justify-center" aria-label="Advertisement">
+            <AdImage ad={shuffle(ADS_728X90)[0]} page="technology" />
+          </div>
+        )}
       </main>
       <Footer />
     </div>