add redpanda to legion cluster

Deploy single-broker Redpanda in dedicated namespace with 20Gi storage,
1 CPU / 2Gi memory limits, and a one-shot topic init job for neuron.swarm,
neuron.ci, neuron.vcs, and neuron.webhooks with appropriate retention.

servers/legion/k8s/redpanda/pvc.yaml

@@ -2,11 +2,11 @@ apiVersion: v1
 kind: PersistentVolumeClaim
 metadata:
   name: redpanda-data
-  namespace: platform
+  namespace: redpanda
 spec:
   storageClassName: local-path
   accessModes:
     - ReadWriteOnce
   resources:
     requests:
-      storage: 10Gi
+      storage: 20Gi