Make Dataset Viewer drafts revision-safe #1635

Description

Make Dataset Viewer annotation and label drafts principal-scoped and revision-safe so stale browser state cannot overwrite newer server data or cross authenticated-user boundaries. Replace the dormant offline synchronization path with explicit local draft recovery and conflict handling.

Acceptance Criteria

• Annotation and label reads return strong revisions and mutations require matching preconditions.
• Local and Azure storage reject stale updates and deletes with current revision context.
• Browser drafts include opaque principal scope, resource identity, baseline, ETag, generation, and timestamp.
• Hydration and conflict resolution reject stale generations and support deterministic merges.
• Obsolete offline queue stores, hooks, and UI are removed without losing local draft recovery.
• Backend and frontend tests cover ownership, stale writes, migration, and recovery behavior.

Related

• Evidence source: comprehensive accessibility and data-integrity review
• Scope: Dataset Viewer backend and frontend persistence only