Istio mesh security

Use the package’s networking and mesh guidance for the Console and Defender traffic boundaries, and Granting Egress to Blocked Services for current diagnostics and a supported external-destination example.

The chart uses bb-common interfaces under istio, routes, and networkPolicies, not the legacy istio.hardened configuration from the old shared guide. See the bundled bb-common 1.6.0 Istio guide, matching the version to Chart.yaml.