fix: hide the add button when the folder is a knowledge base (#765)

### What problem does this PR solve?

#764 fix: hide the add button when the folder is a knowledge base

### Type of change

- [x] Bug Fix (non-breaking change which fixes an issue)

web/src/interfaces/database/file-manager.ts

@@ -28,4 +28,5 @@ export interface IFolder {
   type: string;
   update_date: string;
   update_time: number;
+  source_type: string;
 }