Import Inventory Nodes

Create or update inventory nodes in bulk. Optionally assign them to a cluster.

This is an upsert. The service matches a node by (name, siteId). For an existing node, it overwrites the host vars. With ansible_groups, it replaces the cluster additional.ansibleGroups. Because the operation is an upsert, both inventory:create and inventory:update are required and scoped to clusterId. The audit records the acting admin. The prime-admin import command also needs inventory:read for resolution and collision preflight.