fix(#1003): fallback to draft version on dataset page when no version…

[Janvi-kapoor]

What this PR does / why we need it:

When accessing a dataset page without an explicit version query parameter, the repository defaults to fetching :latest-published. For draft-only datasets, this request returns a 404 error, preventing authorized users (such as creators accessing datasets from notifications) from viewing their draft dataset.

This PR updates DatasetJSDataverseRepository.getByPersistentId:

• When no requestedVersion is provided and the initial :latest-published request fails, it attempts a fallback to :draft.
• If the :draft request also fails (e.g. for unauthorized users lacking draft-view permissions), it throws the error normally.
• If an explicit version was requested, existing behavior remains unchanged.

Which issue(s) this PR closes:

• Closes Dataset Page: show "only draft" version if user has permission #1003

Special notes for your reviewer:

• Handled at the repository layer (DatasetJSDataverseRepository) as discussed in the issue thread.
• Preserves existing fallback logic when explicit versions are supplied.

Suggestions on how to test this:

1. Create a draft-only dataset.
2. Navigate to the dataset URL without a version query parameter (/datasets?persistentId=<doi>).
3. Verify that the draft version loads successfully for authorized users instead of throwing a 404 error.
4. Access the same URL as an anonymous/unauthorized user and verify that the request fails as expected.

Does this PR introduce a user interface change? If mockups are available, please link/include them here:

No.

Is there a release notes or changelog update needed for this change?:

Yes, updated CHANGELOG.md under [Unreleased] -> ### Fixed.

Additional documentation:

None.