close AI-246, AI-285
<!-- This is an auto-generated comment: release notes by coderabbit.ai
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## Summary by CodeRabbit
## Summary by CodeRabbit
* **New Features**
* Introduced an AI chat interface accessible from the sidebar with a
dedicated "/chat" route.
* Added "AFFiNE Intelligent" button with AI icon to the sidebar for
quick chat access.
* Enhanced chat components with an "independent mode" for improved
message display and layout.
* Improved chat input and content styling, including responsive layout
and onboarding offset support.
* **Improvements**
* Expanded icon support to include an AI icon in the app.
* Updated utility and schema functions for greater flexibility and error
prevention.
* Added a new chat container style for consistent layout and max width.
* **Bug Fixes**
* Prevented potential errors when certain editor hosts are not provided.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->
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