fix(server): doc embedding crash with transaction (#13042)

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

## Summary by CodeRabbit

* **Chores**
* Improved reliability of certain workspace operations to ensure
consistency during processing.

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

packages/backend/server/src/models/copilot-workspace.ts

@@ -16,6 +16,7 @@ import type {
 
 @Injectable()
 export class CopilotWorkspaceConfigModel extends BaseModel {
+  @Transactional()
   private async listIgnoredDocIds(
     workspaceId: string,
     options?: PaginationInput