[BUG] <title>Feature Request: Preserve or Warn About Guest Chat History Loss on Login

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是否已有关于该错误的issue或讨论？ | Is there an existing issue / discussion for this?

• 我已经搜索过已有的issues和讨论 | I have searched the existing issues / discussions

该问题是否在FAQ中有解答？ | Is there an existing answer for this in FAQ?

• 我已经搜索过FAQ | I have searched FAQ

当前行为 | Current Behavior

When using the chat as a guest, all conversation history is stored locally in the browser. But as soon as I log in to my account, this guest history disappears completely—with no warning. I lost a long, carefully crafted dialogue this way, and it felt like unexpected data loss.

期望行为 | Expected Behavior

1. When using Qwen Chat as a guest, please add a small, persistent note below each AI response (near the "Copy" / "Share" buttons), for example:
   You’re not signed in. Your chat history will not be saved.
   This helps users understand the risk of data loss in context, without pop-ups or UI changes — just a gentle reminder where they’re already looking.

2. Show a warning before login:
   “Logging in will clear your guest chat history. Would you like to copy it first?”

3. Automatically migrate guest history to the user account (if technically feasible).

4. I propose adding a small, non-intrusive panel on the left sidebar (where chat history appears for logged-in users) that shows:
   You’re in guest mode
   Your chats are saved only in this browser.
   Sign in to save conversations permanently and sync across devices.

复现方法 | Steps To Reproduce

No response

运行环境 | Environment

Web site - https://chat.qwen.ai/

备注 | Anything else?

No response