perf: optimize embed mode

[qianphong]

What this PR does / why we need it?

When embedding with http://localhost:3000/ui/chat/{token}?mode=embed into a third party, there should be no space left in the top right corner. The position of the history button is incorrect. I expect the display to be optimized for standalone embedding.

Summary of your change

I've added a route parameter ?mode=embed&popup=no to determine whether the content is displayed in a popup. There is no impact on the Floating Mode.

<!-- before -->
http://localhost:3000/ui/chat/{token}?mode=embed
<!-- after -->
http://localhost:3000/ui/chat/{token}?mode=embed&popup=no

Please indicate you've done the following:

• Made sure tests are passing and test coverage is added if needed.
• Made sure commit message follow the rule of Conventional Commits specification.
• Considered the docs impact and opened a new docs issue or PR with docs changes if needed.

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