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>

apps/web/package.json

@@ -12,10 +12,12 @@
     "@afterlife/shared": "*",
     "framer-motion": "^12.34.3",
     "howler": "^2.2.4",
+    "mercadopago": "^2.12.0",
     "next": "^15",
     "next-intl": "^4.8.3",
     "react": "^19",
-    "react-dom": "^19"
+    "react-dom": "^19",
+    "uuid": "^13.0.0"
   },
   "devDependencies": {
     "@tailwindcss/postcss": "^4",