Fix theme consistency, i18n completeness, CSS variable naming, and hardcoded strings

src/app/admin/page.tsx

@@ -103,7 +103,7 @@ export default async function AdminDashboard() {
           ) : (
             <div className="space-y-0">
               {activity.map((a, i) => (
-                <div key={String(a.id)} className={`flex items-center gap-3 py-2.5 ${i > 0 ? "border-t border-[var(--border)]" : ""}`}>
+                <div key={String(a.id)} className={`flex items-center gap-3 py-2.5 ${i > 0 ? "border-t border-[var(--border-subtle)]" : ""}`}>
                   <div className="w-7 h-7 rounded-full bg-[var(--color-primary)]/10 grid place-items-center flex-none">
                     <Activity size={12} className="text-[var(--color-primary)]" />
                   </div>