feat: add env vars to allow user config display bot and user icon

[fdb02983rhy]

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Summary

Closes:

• add env vars to allow user config display bot and user icon #22245

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Checklist

• This change requires a documentation update, included: Dify Document
• I understand that this PR may be closed in case there was no previous discussion or issues. (This doesn't apply to typos!)
• I've added a test for each change that was introduced, and I tried as much as possible to make a single atomic change.
• I've updated the documentation accordingly.
• I ran dev/reformat(backend) and cd web && npx lint-staged(frontend) to appease the lint gods

[crazywoola]

Sorry, but we could not accept this from UI/UX side. :(