feat(recharge): USDT 通道改为内嵌二维码模式，替代跳转 pay.g7g7.top

- 接入 qrcodejs2 生成 TRC20 地址二维码
- 充值弹窗内嵌：地址/金额/QR/倒计时，一键复制
- 每 3 秒轮询 /epay_order_status，到账自动关闭 + 刷新余额
- 后端返回 qrcode 字段时走内嵌；若无则回退跳转式（兼容）

package-lock.json

@@ -11,6 +11,7 @@
         "axios": "^0.18.0",
         "babel-preset-es2015": "^6.24.1",
         "px2rem-loader": "^0.1.9",
+        "qrcodejs2": "^0.0.2",
         "swiper": "^4.5.0",
         "vue": "^2.5.2",
         "vue-js-cookie": "^2.1.0",
@@ -11619,6 +11620,12 @@
         "teleport": ">=0.2.0"
       }
     },
+    "node_modules/qrcodejs2": {
+      "version": "0.0.2",
+      "resolved": "https://registry.npmjs.org/qrcodejs2/-/qrcodejs2-0.0.2.tgz",
+      "integrity": "sha512-+Y4HA+cb6qUzdgvI3KML8GYpMFwB24dFwzMkS/yXq6hwtUGNUnZQdUnksrV1XGMc2mid5ROw5SAuY9XhI3ValA==",
+      "license": "MIT"
+    },
     "node_modules/qs": {
       "version": "6.11.0",
       "resolved": "https://registry.npmjs.org/qs/-/qs-6.11.0.tgz",