feat(core): add an independent AI panel (#13004)

close AI-246, AI-285
<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## 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 -->

packages/frontend/core/src/modules/workbench/constants.tsx

@@ -1,4 +1,5 @@
 import {
+  AiIcon,
   AllDocsIcon,
   AttachmentIcon,
   DeleteIcon,
@@ -22,6 +23,7 @@ export const iconNameToIcon = {
   trash: <DeleteIcon />,
   attachment: <AttachmentIcon />,
   pdf: <ExportToPdfIcon />,
+  ai: <AiIcon />,
 } satisfies Record<string, ReactNode>;
 
 export type ViewIconName = keyof typeof iconNameToIcon;