[账单] 「本对话费用」应显示人民币 (与账户额度货币一致)

**提交人**: 用户1727
**客户端版本**: 0.1.16

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## 使用场景
账户额度以人民币计算(如赠送的 20 元),但对话框右下角「本对话费用」以美元(\$)显示。单位不一致,用户无法直观对照自己的额度消耗,需要额外换算才能知道花了多少钱。

## 诉求
让「本对话费用」以人民币显示,或与用户账户额度的货币单位保持一致,方便用户直接对照。
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**OS**: win32 x64 (10.0.26200)
**界面语言**: zh-CN

The issue does not name a file, test, or entry point. Start by locating the UI that renders “本对话费用” and the code that provides the account quota currency. Done means the conversation cost uses人民币 or otherwise matches the account quota currency, with the relevant display behavior covered by an existing or new test.

Written by the indexing model from the issue text.