Reapply "Add missing admin action files and navigation links"

This reverts commit 4d515bc400.

src/actions/article-reactions.ts

@@ -31,7 +31,9 @@ export async function toggleReaction(formData: FormData): Promise<void> {
   const userId = Number(session.user.id);
   if (!Number.isFinite(userId)) return;
 
-  const reaction = String(formData.get("reaction") ?? "").trim().toLowerCase();
+  const reaction = String(formData.get("reaction") ?? "")
+    .trim()
+    .toLowerCase();
   if (!ALLOWED_REACTIONS.has(reaction)) return;
 
   const articleIdRaw = String(formData.get("articleId") ?? "").trim();