i18n: update zh-CN translation for login label

[JesseAtSZ]

Refined the translation for "login" from "登录" (Login) to "账号" (Account/Login ID) in admin.json to better describe the input field.

In Chinese, "登录" (Login) is primarily used as a verb for action buttons. Since this field refers to the user's credential or identifier, "Username" or "Account" (账号) is a more accurate and contextually appropriate term.

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