Upload mags+attachments to existing dataset, adapt to wk api 14

[fm3]

Description:

• Corresponding wk PR Allow uploading mags, attachments to existing datasets webknossos#9402

Issues:

• fixes #...

Todos:

• clean up
• other mag properties (axis_order, channelIndex?)
• use v14 versioned routes during upload
• tests
• backwards compatibility for servers that only have v13? https://scm.slack.com/archives/C02Q35Q28P5/p1775551705974079

Make sure to delete unnecessary points or to check all before merging:

• Updated Changelog
• Updated Documentation
• Added / Updated Tests
• Considered adding this to the Examples

[gemini-code-assist]

Code Review

This pull request updates the dataset upload process to align with API version 14, including refactoring upload models and updating API routes. It introduces ApiDatasetUploadInfo and ApiResumableUploadInfo while simplifying the parameters for finishing and reserving uploads. A review comment recommends using datastore_api_client.url_prefix for the Resumable upload URL to maintain consistency with the versioned API.