Drop ZFS-replication as an interim HA step; jump straight to Ceph

Simplifies the storage model to one long-term tier (Ceph) instead of
two. Node 1 runs local ZFS only until nodes 2/3 join, at which point
Ceph goes live and VMs migrate onto it directly.

README.md

@@ -9,11 +9,12 @@ hardware, with the end goal of a 3-node HA cluster.
   forced disabling hardware-accelerated virtualization — not expected to
   recur on new hardware; verify VT-x/AMD-V + IOMMU in BIOS before assuming
   otherwise).
-- Move off LVM-thin to ZFS for local storage.
+- Move off LVM-thin to ZFS for local (boot + pre-cluster) storage.
 - Build node 1 so its disk and network layout doesn't need rework when nodes
   2 and 3 are added later.
 - End state: 3-node cluster, quorum via corosync, HA-managed VMs backed by
-  ZFS replication and/or Ceph.
+  Ceph. No intermediate ZFS-replication HA step — Ceph goes live as soon as
+  node 2/3 join.
 
 ## Repo layout