fix(data): remove empty data field from OpenBao placeholder Secret

kubectl apply --server-side was managing the `data: {}` field, which
caused it to wipe the key/root-token entries written by the seed script
on subsequent applies. Removing the field entirely means server-side
apply never touches data, so seed-written keys survive re-applies.

base/data/openbao-keys-placeholder.yaml

@@ -1,9 +1,10 @@
-# Placeholder secret — replaced by the init script after `bao operator init`.
+# Placeholder secret — seed script writes real key/root-token data after init.
-# Exists so the auto-unseal sidecar's volume mount doesn't block pod startup.
+# Exists so the auto-unseal sidecar volume mount doesn't block pod startup.
+# `data` is intentionally omitted so server-side apply never manages (or wipes)
+# the key fields written by the seed script.
 apiVersion: v1
 kind: Secret
 metadata:
   name: openbao-keys
   namespace: data
 type: Opaque
-data: {}