Add rate limiting for export

**Feature request**
It would be great to have search for middleware.

**Use case**
Many users need this functionality for production deployments.

**Implementation idea**
Add a new config option `enable_search` with default `false`.

First reconcile the title's export rate-limiting request with the body’s middleware search request and the `enable_search` configuration idea. Locate the middleware, configuration handling, and export-related entry points, then confirm the intended behavior and acceptance criteria before making changes.

Written by the indexing model from the issue text.