articles/[slug]: drop Stay Updated sidebar card; related fallback to latest

Empty Related Articles bug on /articles/<slug> traced to two issues:
- Two rows were imported with category="industry" instead of the canonical
  "Industry News", so the category-match query returned zero peers.
- The fallback path was missing — getLegacyRelatedArticles now tops up
  with the latest published rows whenever the category match is short.

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

src/app/articles/[slug]/ArticleDetailClient.tsx

@@ -424,17 +424,6 @@ export default function ArticleDetailClient({ article, relatedArticles }: Articl
               </div>
             </div>
 
-            {/* Newsletter Signup */}
-            <div className="bg-[#0d1520] border border-[#1e3a5f] p-5">
-              <h3 className="font-heading text-[#e0e0e0] font-bold mb-2">Stay Updated</h3>
-              <p className="font-body text-[#777] text-xs mb-4">
-                Get the latest broadcast engineering news delivered to your inbox.
-              </p>
-              <Link href="/home-page#newsletter" className="btn-subscribe text-xs py-2 px-4 inline-block w-full text-center">
-                Subscribe Free
-              </Link>
-            </div>
-
             {/* Sidebar ad stack — 300x600 + 300x250 rotating */}
             <SidebarAdStack />
           </aside>

src/lib/articles/legacy-source.ts

@@ -252,21 +252,42 @@ export async function getLegacyRelatedArticles(
   category: string | null,
   count: number,
 ): Promise<Article[]> {
-  try {
-    let q = client()
-      .from("wp_imported_posts")
-      .select(SELECT_COLS)
-      .eq("status", "published")
-      .neq("wp_slug", excludeSlug)
-      .order("wp_published_at", { ascending: false })
-      .limit(count);
-    if (category) q = q.eq("category", category);
-    const { data, error } = await q;
-    if (error || !data) return [];
-    return (data as ImportedPostRow[]).map((r) => rowToArticle(r));
-  } catch {
-    return [];
+  const collected: ImportedPostRow[] = [];
+  const seen = new Set<string>([excludeSlug]);
+  // First pass: same category. Skip when no category recorded.
+  if (category) {
+    try {
+      const { data } = await client()
+        .from("wp_imported_posts")
+        .select(SELECT_COLS)
+        .eq("status", "published")
+        .eq("category", category)
+        .neq("wp_slug", excludeSlug)
+        .order("wp_published_at", { ascending: false })
+        .limit(count);
+      for (const row of (data as ImportedPostRow[] | null) || []) {
+        if (!seen.has(row.wp_slug)) { collected.push(row); seen.add(row.wp_slug); }
+      }
+    } catch {}
   }
+  // Fallback: top up to `count` with the latest published, excluding what we
+  // already have. Handles tiny categories, orphan rows, and category=null.
+  if (collected.length < count) {
+    try {
+      const { data } = await client()
+        .from("wp_imported_posts")
+        .select(SELECT_COLS)
+        .eq("status", "published")
+        .neq("wp_slug", excludeSlug)
+        .order("wp_published_at", { ascending: false })
+        .limit(count + collected.length + 5);
+      for (const row of (data as ImportedPostRow[] | null) || []) {
+        if (collected.length >= count) break;
+        if (!seen.has(row.wp_slug)) { collected.push(row); seen.add(row.wp_slug); }
+      }
+    } catch {}
+  }
+  return collected.map((r) => rowToArticle(r));
 }
 
 export async function getLegacyArticlesBySection(