Tienda Battlepay: pago de órdenes pendientes vía Stripe

Reutiliza la infraestructura Stripe (sin depender de SumUp/credenciales externas):
- lib/battlepay.ts: getPendingOrders/getPendingOrder/markOrderPaid sobre
  acore_auth.battlepay_orders (PENDING->PAID, el mod-battlepay entrega en juego).
- fulfill.ts: rama battlepay (metadata.battlepay_reference -> markOrderPaid),
  idempotente vía el claim atómico compartido con el webhook.
- API POST /api/battlepay/pay (valida orden PENDING de la cuenta, crea checkout).
- UI: /battlepay (lista + pagar) y /battlepay-success (entrega compartida),
  enlace "Tienda" en la cabecera para usuarios logueados.
- i18n es/en: namespace Battlepay + Nav.store.

Verificado: build OK, /battlepay 307->login, API 401 sin sesión, success 200.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

web-next/app/[locale]/battlepay-success/page.tsx

@@ -0,0 +1,45 @@
+import { getTranslations, setRequestLocale } from 'next-intl/server'
+import { Link } from '@/i18n/navigation'
+import { fulfillCheckoutSession } from '@/lib/fulfill'
+import { isSessionPaid } from '@/lib/stripe'
+
+export const dynamic = 'force-dynamic'
+
+export default async function BattlepaySuccessPage({
+  params,
+  searchParams,
+}: {
+  params: Promise<{ locale: string }>
+  searchParams: Promise<{ session_id?: string }>
+}) {
+  const { locale } = await params
+  setRequestLocale(locale)
+  const { session_id } = await searchParams
+  const t = await getTranslations('Battlepay')
+
+  // Entrega compartida con el webhook (marca la orden PAID; idempotente).
+  let status: 'paid' | 'already' | 'error' = 'error'
+  if (session_id) {
+    const r = await fulfillCheckoutSession(session_id)
+    if (r.ok) status = 'paid'
+    else if (await isSessionPaid(session_id)) status = 'already'
+  }
+
+  return (
+    <main className="mx-auto max-w-lg px-4 py-12 text-center">
+      <h1 className="mb-6 text-2xl font-bold text-amber-500">{t('title')}</h1>
+      {status === 'paid' ? (
+        <p className="text-green-400">{t('paidOk')}</p>
+      ) : status === 'already' ? (
+        <p className="text-green-400">{t('alreadyPaid')}</p>
+      ) : (
+        <p className="text-red-400">{t('genericError')}</p>
+      )}
+      <p className="mt-6">
+        <Link href="/battlepay" className="text-sky-400 hover:underline">
+          ← {t('backToStore')}
+        </Link>
+      </p>
+    </main>
+  )
+}