Revert "Add missing admin action files and navigation links"

This reverts commit 41be6835bf.

src/app/admin/achievements/page.tsx

@@ -53,9 +53,7 @@ export default async function AdminAchievements() {
         </div>
         <div>
           <h1 className="m-0 text-xl font-extrabold text-[var(--color-text)]">{t("title")}</h1>
-          <p className="m-0 text-xs text-[var(--color-text-muted)] mt-0.5">
-            {t("subtitle", { rows: achievements.length, categories: groups.size })}
-          </p>
+          <p className="m-0 text-xs text-[var(--color-text-muted)] mt-0.5">{t("subtitle", { rows: achievements.length, categories: groups.size })}</p>
         </div>
       </div>
 
@@ -72,9 +70,7 @@ export default async function AdminAchievements() {
           <section key={category} className="mt-6">
             <h2 className="admin-section-title">
               {category}{" "}
-              <span className="inline-block text-[0.72rem] font-bold px-2 py-0.5 rounded-full bg-[var(--color-primary)]/18 text-[var(--color-text)]">
-                {rows.length}
-              </span>
+              <span className="inline-block text-[0.72rem] font-bold px-2 py-0.5 rounded-full bg-[var(--color-primary)]/18 text-[var(--color-text)]">{rows.length}</span>
             </h2>
             <div className="admin-card p-0 overflow-x-auto">
               <table>