python(feat): annotations resource

[Brandon-Shippy]

Description

Adds an annotations resource to sift_client, covering data reviews, phases, and the review history.

• AnnotationsAPIAsync with the usual get, list_, find, create, update, archive, unarchive, plus batch archive. Wired up as client.annotations
• AnnotationLogsAPIAsync nested as client.annotations.logs
• AnnotationsLowLevelClient wraps AnnotationService; the high-level client has zero proto imports
• Pydantic models in sift_types/annotation.py
• create_review(...) and create_phase(...) alongside create. Passing channels derives the asset
• resolve(), flag(), reopen(), assign(), comment() on the resource and the Annotation
• Sync wrappers and type stubs registered

Validation

• End to End testing with manual script written to test each new API feature.
• Verified against a local stack, including the annotation rendering in Explore

[github-actions]

Python docs preview: https://sift-stack.github.io/sift/python/pr-792/

Deployed from 6bda0aa. The link may take up to a minute to become live as GitHub Pages propagates.