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

src/i18n/locales/en.json

@@ -53,7 +53,9 @@
     "error_loading_districts": "Error loading districts. Please try again.",
     "error_loading_categories": "Error loading categories. Please try again.",
     "error_loading_product": "Error loading product details. Please try again.",
-    "not_found": "Location not found. Returning to previous menu."
+    "not_found": "Location not found. Returning to previous menu.",
+    "mono_product": "📦 Digital Product",
+    "infinite_stock": "∞ Always available"
   },
   "purchase": {
     "summary": "🛒 Purchase Summary:",
@@ -103,7 +105,7 @@
     "address": "Address",
     "network": "Network",
     "deposit": "💳 Deposit {{type}}",
-    "deposit_via_changenow": "💳 Deposit via ChangeNOW",
+    "deposit_via_crypto": "💳 Deposit via Crypto",
     "select_crypto": "🔐 Select cryptocurrency to generate wallet:",
     "wallet_generated": "✅ New wallet generated successfully!",
     "wallet_type": "Type",
@@ -153,22 +155,28 @@
     "next_page": "➡️ Next",
     "wallet_not_found": "Wallet not found. Please try again.",
     "wallet_not_found_short": "Wallet not found.",
-    "deposit_changenow_select": "💳 *Deposit via ChangeNOW*\n\nSelect the wallet you want to top up:",
+    "deposit_select_gateway": "💳 *Deposit via Crypto*\n\nSelect the wallet you want to top up:",
     "deposit_select_amount": "💳 *Deposit {{type}}*\n\nSelect the amount (USD) you want to deposit:",
     "deposit_title": "💳 *Deposit {{type}} — €{{amount}}*",
     "deposit_instructions_title": "📋 *Step\\-by\\-step instructions:*",
     "deposit_step1": "1️⃣ Tap *Copy Address* below to copy your wallet address",
-    "deposit_step2": "2️⃣ Tap *Open ChangeNOW* \\— the amount €{{amount}} and currency {{type}} are already set",
-    "deposit_step3": "3️⃣ On ChangeNOW\\, paste the copied address as the receiving wallet",
-    "deposit_step4": "4️⃣ Enter your email and create a password when prompted \\— this is *required by law* for card payments \\(KYC verification\\)\\. Your data is protected by ChangeNOW\\'s security",
-    "deposit_step5": "5️⃣ Pay with your bank card \\(Visa\\/Mastercard\\)",
+    "deposit_step2": "2️⃣ Open Mercuryo via the button below",
+    "deposit_step3": "3️⃣ Paste the copied address as the receiving wallet",
+    "deposit_step4": "4️⃣ Select the correct currency: *{{type}}* and the amount €{{amount}}",
+    "deposit_step5": "5️⃣ Complete the payment with your bank card",
     "deposit_step6": "6️⃣ Crypto will arrive in your wallet within 5\\-30 minutes",
     "deposit_your_address": "🔐 *Your {{type}} wallet address:*",
     "deposit_important_title": "⚠️ *Important:*",
     "deposit_important1": "• Double\\-check the wallet address before confirming",
-    "deposit_important2": "• Email \\+ password on ChangeNOW is a standard verification step for card payments \\— don\\'t worry\\, it\\'s safe",
-    "deposit_important3": "• If crypto doesn\\'t arrive within 30 min \\— check the transaction status in your ChangeNOW email confirmation",
-    "deposit_open_changenow": "🌐 Open ChangeNOW — €{{amount}} → {{type}}",
+    "deposit_important2": "• Make sure you select the correct currency in Mercuryo",
+    "deposit_important3": "• Email \\+ phone may be required by Mercuryo for verification",
+    "deposit_important4": "• If crypto doesn't arrive within 30 min \\— contact Mercuryo support",
+    "deposit_open_mercuryo": "💳 Mercuryo",
+    "deposit_pay_crypto": "💰 Pay with Crypto",
+    "deposit_crypto_title": "💳 *Deposit {{type}} via Crypto*",
+    "deposit_crypto_address": "🔐 *Your {{type}} wallet address:*",
+    "deposit_crypto_instruction": "Send {{amount}} USD in {{type}} to the address above. The QR code contains the payment address.",
+    "deposit_crypto_scan_qr": "📱 Scan the QR code below to get the wallet address",
     "deposit_copy_address": "📋 Copy Address",
     "deposit_change_amount": "🔄 Change Amount",
     "deposit_choose_different": "💸 Choose Different Wallet",