chore: define view model (#12949)

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

* **New Features**
* Introduced a chat interface with message list, empty state view, and
support for user, assistant, and system messages.
* Added a chat manager for session and message handling, including
session creation, message sending, and error management.
* Implemented various chat cell types (attachments, context references,
workflow status, loading, and error cells) with corresponding data
models and view models.
* Enabled asynchronous message sending from the input box with error
alerts and automatic session creation.
* Added workflow and context-related models for advanced chat features.

* **Enhancements**
* Improved UI responsiveness with table view updates and dynamic empty
state handling.
  * Provided a method to clear all attachments in the input box.

* **Bug Fixes / Style**
* Refined code formatting, access control, and minor stylistic
improvements across multiple files for consistency.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

packages/frontend/apps/ios/App/Packages/AffineGraphQL/Sources/Schema/CustomScalars/JSONObject.swift

@@ -39,4 +39,3 @@ public enum CustomJSON: CustomScalarType, Hashable {
     hasher.combine(_jsonValue)
   }
 }
-