Enhance TopUpModal styling and update localization files

- Updated button styles in TopUpModal for improved visual feedback during interactions.
- Adjusted modal positioning for better user experience on desktop.
- Added 'paymentMethod' key to localization files for English, Persian, Russian, and Chinese languages, enhancing multi-language support.

src/locales/zh.json

@@ -185,6 +185,7 @@
     "topUp": "充值",
     "topUpBalance": "充值余额",
     "enterAmount": "输入金额",
+    "paymentMethod": "支付方式",
     "paymentMethods": {
       "yookassa": {
         "name": "YooKassa",