fix: 修复分站充值页面所有支付按钮不可用的问题

- EPay: 改用隐藏表单POST提交（与主站一致），修复参数缺失错误
- Stripe: 修正响应字段为 data.pay_link，使用 window.open 打开
- Crypto: 新增链(TRON/ETH/BSC)和代币(USDT/USDC)选择器，发送完整参数
- Creem: 改为产品模式，展示产品卡片，发送 product_id 而非 amount
- 新增相关 i18n 翻译键

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/i18n/locales/en.json

@@ -189,6 +189,13 @@
     "topup.amount": "Amount",
     "topup.chain": "Chain",
     "topup.waitingPayment": "Waiting for payment...",
-    "topup.close": "Close"
+    "topup.close": "Close",
+    "topup.selectChain": "Please select a blockchain network",
+    "topup.selectToken": "Please select a token",
+    "topup.token": "Token",
+    "topup.payWith": "Pay with",
+    "topup.payNow": "Pay",
+    "topup.quotaIncluded": "{{count}} quota included",
+    "topup.creemPayment": "Creem Payment"
   }
 }

src/i18n/locales/zh.json

@@ -189,6 +189,13 @@
     "topup.amount": "金额",
     "topup.chain": "链",
     "topup.waitingPayment": "等待支付中...",
-    "topup.close": "关闭"
+    "topup.close": "关闭",
+    "topup.selectChain": "请选择区块链网络",
+    "topup.selectToken": "请选择代币",
+    "topup.token": "代币",
+    "topup.payWith": "使用",
+    "topup.payNow": "支付",
+    "topup.quotaIncluded": "含 {{count}} 额度",
+    "topup.creemPayment": "Creem 支付"
   }
 }