feat(server): add morph doc edit tool (#12789)

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

- **New Features**
- Introduced support for the Morph provider in the copilot module,
enabling integration with the Morph LLM API.
- Added a new document editing tool that allows users to propose and
apply edits to existing documents via AI assistance.
- **Configuration**
- Added configuration options for the Morph provider in both backend and
admin interfaces.
- **Enhancements**
- Expanded tool support to include document editing capabilities within
the copilot feature set.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

packages/backend/server/src/plugins/copilot/tools/index.ts

@@ -1,3 +1,4 @@
+export * from './doc-edit';
 export * from './doc-keyword-search';
 export * from './doc-semantic-search';
 export * from './error';