Determine memory requirements for download

The current download logic may be importing the entire file into memory here:

https://github.com/Imageomics/dataverse-access/blob/7a67502d5a2fc87e3902982dd42690fbbbde9cce/dv.py#L73-L74

Determine if there is a streaming approach to reduce requirements.

Start by inspecting the download logic in dv.py at lines 73-74 and determine whether the current operation loads the entire file into memory. Investigate whether the existing command-line download path supports streaming, then verify that the chosen approach reduces memory requirements without changing download behavior.

Written by the indexing model from the issue text.