Optimize build by separating development and production fixtures

## Description
Currently, the production bundle includes all test fixtures, which unnecessarily increases the artifact size for the live website deployment.

### Proposed Solution
Separate the build process to optimize the production output:
* **Dev Build:** Include all available fixtures for local testing and development.
* **Production Build:** Bundle *only* the fixtures located in `/fixtures/preview-service`.

Start by locating the build configuration and the code that includes fixtures, then compare the development and production build paths. Confirm that development still includes all fixtures while production bundles only /fixtures/preview-service, and verify the resulting production artifact size or contents.

Written by the indexing model from the issue text.