Dicom import

Currently the app requires nifti or bids data.

For dicoms, one option could be to supply a formatted dicom zip, e.g.:
```{subject}_{session}.zip```
(the upstream app could create the dicom zip from uploaded files and metadata)

Given this, then this workflow would need to:
- parse subject, session from the filename
- extract files, convert to nifti
- figure out what files are T1w and what are DWI, and ignore anything else
- rest of the workflow identical

No files, tests, or entry points are named in the issue. Start by locating the existing NIfTI/BIDS workflow, then compare it with the proposed DICOM zip flow: filename parsing, extraction, conversion to NIfTI, T1w/DWI identification, and continuation through the existing workflow. Done means the app accepts the described zip format and preserves the current workflow for the relevant files.

Written by the indexing model from the issue text.