add error/loading/404 boundaries, responsive tables, Metadata API

src/app/[locale]/admin/billing/page.tsx

@@ -98,6 +98,7 @@ export default async function AdminBillingPage() {
         <div className="animate-in animate-in-delay-3">
           <h2 className="text-lg font-semibold mb-3">{t("balancesTitle")}</h2>
           <Card>
+            <div className="overflow-x-auto">
             <table className="w-full text-sm">
               <thead className="text-xs text-text-muted text-left">
                 <tr>
@@ -126,6 +127,7 @@ export default async function AdminBillingPage() {
                 ))}
               </tbody>
             </table>
+            </div>
           </Card>
         </div>
       )}

src/app/[locale]/admin/page.tsx

@@ -5,6 +5,11 @@ import { listTenants } from "@/lib/k8s";
 import { countPendingSkillActivationRequests } from "@/lib/db";
 import { AdminPanel } from "@/components/admin/admin-panel";
 
+export async function generateMetadata() {
+  const t = await getTranslations("common");
+  return { title: t("admin") };
+}
+
 export default async function AdminPage() {
   const user = await getSessionUser();
   if (!user) redirect("/login");