Adopt Longhorn for heterogeneous node storage

[jorisjonkers-dev-agents]

Context. Nodes differ in storage size/speed; not all should host replicas. Plan + roll out Longhorn with tiers, using the existing per-node inventory (incl. GPU-memory scheduling) to place replicas.

Steps

• Define storage tiers / node labels from the inventory (fast-ssd vs bulk vs no-storage nodes).
• Install Longhorn via a platform-blueprints pack; set replica count + node selectors per tier.
• Migrate one non-critical PVC as a pilot; verify replica placement honours the tiers.

Acceptance

• Longhorn healthy; replicas only on storage-capable nodes; pilot volume survives a node drain.