- Upgrade lsdb to 0.10.4 (aligned hats 0.10.4, nested-pandas 0.6.10) across all
  pin sites; no serialization-critical package moved.
- Add a cluster-side lsdb/hats version guard in core/dask.py: distributed's
  get_versions() omits lsdb, so an app/cluster skew was previously silent; the
  guard now queries workers via client.run and fails fast on drift.

No database migrations. DEPLOY NOTE: the Dask cluster (gitops apps/dask) image
tag must advance in lockstep with the app, or the new guard CrashLoops on skew.