fix(storage): consolidate longhorn-kafka → unified longhorn StorageClass

Removes duplicate longhorn-kafka StorageClass managed by Kafka chart.
All applications now use single 'longhorn' StorageClass (3 replicas, Immediate binding).

Changes:
- Kafka chart: use 'longhorn' instead of 'longhorn-kafka'
- Delete Kafka StorageClass template (no longer needed)
- Update longhorn-storageclass.yaml to match deployed config (Immediate, not WaitForFirstConsumer)

Existing Kafka PVCs remain bound to old longhorn-kafka StorageClass (safe - no data loss).
New PVCs will use unified 'longhorn' StorageClass.

k8s/infrastructure/longhorn/longhorn-storageclass.yaml

@@ -10,12 +10,12 @@ metadata:
 provisioner: driver.longhorn.io
 allowVolumeExpansion: true
 reclaimPolicy: Delete
-volumeBindingMode: WaitForFirstConsumer  # Wait for pod scheduling before binding
+volumeBindingMode: Immediate  # Immediate binding for StatefulSets (matches deployed config)
 parameters:
   numberOfReplicas: "3"           # HA across all 3 nodes
   staleReplicaTimeout: "30"
   fromBackup: ""
-  dataLocality: "best-effort"     # Prefer local replica when possible
+  dataLocality: "disabled"        # Match deployed config (not best-effort)
   fsType: "ext4"
   disableRevisionCounter: "true"  # Performance optimization
   unmapMarkSnapChainRemoved: "ignored"