fix(chart): redis address templating

[supreme-gg-gg]

Fixes kagent-dev/kagent#2092

Testing, as suggested in the issue:

helm template kagent charts/substrate -n kagent \
  | grep -E 'ATE_API_REDIS_ADDRESS|name: kagent-valkey-cluster$'
# output: kagent-valkey-cluster.kagent.svc:6379
# old, wrong output: valkey-cluster.kagent.svc:6379

• Tests pass
• Appropriate changes to documentation are included in the PR