Add TypeScript types for services

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

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

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

No files, tests, or entry points are named. Start by locating the service and middleware type definitions and the configuration handling for `enable_export`; clarify what “export for middleware” means and which production deployment behavior is expected. Done should include the new option with a default of `false`, complete TypeScript coverage, and verification that the intended export works.

Written by the indexing model from the issue text.