feat(server): export title and summary on doc resolver (#13139)

close AF-2732






#### PR Dependency Tree


* **PR #13139** 👈

This tree was auto-generated by
[Charcoal](https://github.com/danerwilliams/charcoal)

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

## Summary by CodeRabbit

* **New Features**
* Added support for a document summary field, allowing documents to
include and display an optional summary alongside the title.

* **Bug Fixes**
* Improved access control when retrieving documents, ensuring proper
permission checks are enforced.

* **Tests**
* Expanded test coverage to verify correct handling of document title
and summary fields, including cases where the summary is absent.

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

packages/backend/server/src/schema.gql

@@ -595,6 +595,7 @@ type DocType {
   mode: PublicDocMode!
   permissions: DocPermissions!
   public: Boolean!
+  summary: String
   title: String
   updatedAt: DateTime
   workspaceId: String!