feat: add AFC Store with MercadoPago purchases and prize redemption

Players can now buy AfterCoin with real money (MercadoPago Checkout Pro,
$15 MXN/AFC) and redeem AFC for gift cards or cash withdrawals. Admin
fulfills redemptions manually.

- Bridge: payments + redemptions tables, CRUD routes, PATCH auth
- Next.js API: verify-disk, balance, create-preference, webhook (idempotent
  minting with HMAC signature verification), redeem, payment/redemption history
- Frontend: hub, buy flow (4 packages + custom), redeem flow (gift cards +
  cash out), success/failure/pending pages, history with tabs, 8 components
- i18n: full English + Spanish translations
- Infra: nginx /api/afc/ → Next.js, docker-compose env vars, .env.example

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

docker/docker-compose.dev.yml

@@ -60,10 +60,18 @@ services:
     restart: unless-stopped
     depends_on:
       - cms
+      - afc-bridge
     environment:
       STRAPI_URL: http://cms:1337
       STRAPI_API_TOKEN: ${STRAPI_API_TOKEN:-}
       NEXT_PUBLIC_STRAPI_URL: ${PUBLIC_STRAPI_URL:-http://localhost:1337}
+      AFC_BRIDGE_URL: http://afc-bridge:3001
+      AFC_BRIDGE_SECRET: ${AFC_BRIDGE_SECRET}
+      MERCADOPAGO_ACCESS_TOKEN: ${MERCADOPAGO_ACCESS_TOKEN:-}
+      MERCADOPAGO_WEBHOOK_SECRET: ${MERCADOPAGO_WEBHOOK_SECRET:-}
+      MERCADOPAGO_WEBHOOK_URL: ${MERCADOPAGO_WEBHOOK_URL:-}
+      AFC_PRICE_MXN: ${AFC_PRICE_MXN:-15}
+      NEXT_PUBLIC_SITE_URL: ${NEXT_PUBLIC_SITE_URL:-http://localhost:3000}
     ports:
       - "3000:3000"