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/api/battlepay/pay/route.ts

@@ -0,0 +1,35 @@
+import { getSession } from '@/lib/session'
+import { getPendingOrder } from '@/lib/battlepay'
+import { createCheckoutSession } from '@/lib/stripe'
+
+export async function POST(request: Request) {
+  const session = await getSession()
+  if (!session.accountId) return Response.json({ success: false, error: 'notAuthenticated' }, { status: 401 })
+
+  let b: Record<string, string> = {}
+  try { b = await request.json() } catch { return Response.json({ success: false, error: 'invalidRequest' }, { status: 400 }) }
+  const reference = String(b.reference ?? '').trim()
+  if (!reference) return Response.json({ success: false, error: 'invalidRequest' }, { status: 400 })
+
+  const order = await getPendingOrder(reference, session.accountId)
+  if (!order) return Response.json({ success: false, error: 'orderNotFound' })
+  if (!(order.price_eur > 0)) return Response.json({ success: false, error: 'invalidRequest' })
+
+  const site = process.env.SITE_URL || ''
+  const ip = (request.headers.get('x-forwarded-for') || '').split(',')[0].trim() || '0.0.0.0'
+
+  const r = await createCheckoutSession({
+    accountId: session.accountId,
+    username: session.username || '',
+    email: session.bnetEmail || '',
+    acoreIp: ip,
+    amount: order.price_eur,
+    characterName: reference, // en battlepay guardamos la referencia como identificador
+    productName: order.product_name,
+    successUrl: `${site}/battlepay-success`,
+    cancelUrl: `${site}/battlepay`,
+    metadata: { battlepay_reference: reference },
+  })
+  if (!r.success || !r.url) return Response.json({ success: false, error: 'stripeError' })
+  return Response.json({ success: true, url: r.url })
+}