Integra Battlepay con SumUp (órdenes battlepay_orders)

- pagos_sumup.py: crear_checkout_battlepay(reference,...) y obtener_checkout()
- battlepay_view: lista las órdenes PENDING de la cuenta de juego
- battlepay_pay_view: crea checkout SumUp para una orden concreta (checkout_reference=reference)
- sumup_webhook: marca la orden PAID (valida estado contra la API de SumUp si falta)
- plantillas account/battlepay.html y partials/pago_sumup.html
- sql/battlepay_sumup.sql (tablas battlepay_orders/battlepay_price) y docs actualizados

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

home/urls.py

@@ -77,6 +77,8 @@ urlpatterns = [
     path('guild-success/', views.guild_rename_success_view, name='guild-success'),
     path('guild-cancel/', views.guild_rename_cancel_view, name='guild-cancel'),
     path("pagar-sumup/", views.pagar_sumup, name="pagar_sumup"),
+    path("battlepay/", views.battlepay_view, name="battlepay"),
+    path("battlepay/pay/", views.battlepay_pay_view, name="battlepay_pay"),
     path("sumup-webhook/", views.sumup_webhook, name="sumup_webhook"),
     
 ]