feat: Mercuryo gateway, crypto QR deposit, mono products, wallet auto-refresh

- Replace Quickex/Guardarian with Mercuryo (https://mercuryo.io/)
- Add crypto QR code payment option in deposit flow (qrcode package)
- Add is_mono product flag for digital/infinite products
- Mono products: no quantity buttons in bot, always available
- Admin wallet page: auto-refresh balances from blockchain APIs
- Migration 010: add is_mono column to products
- i18n updates for en/de/es

package.json

@@ -26,6 +26,7 @@
     "node-telegram-bot-api": "^0.64.0",
     "pino": "^8.21.0",
     "pino-pretty": "^13.1.3",
+    "qrcode": "^1.5.4",
     "tiny-secp256k1": "^2.2.3"
   },
   "devDependencies": {