feat: support pod host aliases

[sionsmith]

Summary

• add spec.template.pod.hostAliases support for KafkaBackup and KafkaRestore pods
• use typed Kubernetes HostAlias schema validation instead of a free-form pass-through array
• apply aliases to one-shot backup Jobs, scheduled backup CronJobs, and restore Jobs
• regenerate CRDs and update examples/docs/changelog

Fixes #22.

Validation

• cargo fmt --all -- --check
• cargo test
• cargo clippy --all-targets --all-features -- -D warnings
• helm template --include-crds strimzi-backup-operator deploy/helm/strimzi-backup-operator
• helm lint deploy/helm/strimzi-backup-operator
• git diff --check
• minikube API-server validation for valid and invalid hostAliases
• live local operator reconcile validated generated Job and CronJob pod templates
• runtime canary pod validated Kubernetes /etc/hosts injection