添加信用额度功能：在账户模型中新增信用额度字段，更新相关请求和响应结构，修改账户创建和修改逻辑，更新界面以支持信用额度的显示和编辑。

src/locales/en.json

@@ -1860,6 +1860,8 @@
     "Balance Time": "Balance Time",
     "Sub-account Balance Time": "Sub-account Balance Time",
     "Statement Date": "Statement Date",
+    "Credit Limit": "Credit Limit",
+    "Available": "Available",
     "Description": "Description",
     "Your account description (optional)": "Your account description (optional)",
     "Your sub-account description (optional)": "Your sub-account description (optional)",

src/locales/zh_Hans.json

@@ -1860,6 +1860,8 @@
     "Balance Time": "余额时间",
     "Sub-account Balance Time": "子账户余额时间",
     "Statement Date": "账单日",
+    "Credit Limit": "信用额度",
+    "Available": "可用额度",
     "Description": "描述",
     "Your account description (optional)": "你的账户描述 (可选)",
     "Your sub-account description (optional)": "你的子账户描述 (可选)",