Remove requirement to provide a date range when requesting an export using the Core API.

🔍 Problem Statement

The Core API requires a date range for all export requests, even when the client wants to export the entire dataset. This forces developers to pass an artificially wide date range, which is unintuitive and may miss edge cases.

💡 User Story

As a developer, I want export API requests to work without a mandatory date range, so that I can export the full dataset when no time filter is needed.

🎯 Definition of Done (DoD)

A feature is done when:

✔️ Given an export API request, when no date range is provided, then the full dataset is exported — and existing date-range filtering continues to work when specified.