feat: add nodeSelector support for scheduled task scopes

[fedemaleh]

Summary

Adds nodeSelector support to the scheduled task (CronJob) deployment template, closing a gap with the k8s deployment template which already supported it. tolerations was already supported in both templates; only nodeSelector was missing from scheduled tasks.

Changes

• scheduled_task/deployment/templates/deployment.yaml.tpl: render a nodeSelector block from k8s_modifiers.deployment.nodeselector, mirroring the existing tolerations block and sharing the same {{- if $deployment }} guard.
• CHANGELOG.md: entry under [Unreleased].

Notes

• The modifier field key is lowercase nodeselector (the platform's modifier name), rendered to the k8s-canonical nodeSelector: key — same convention as the k8s deployment template.
• Uses indent 10 (not 8) because the CronJob nests the pod spec under jobTemplate → spec → template → spec, matching the sibling tolerations block.
• No values.yaml change needed — k8s_modifiers are injected by the platform at render time.

Test plan

• Deploy a scheduled task scope with a deployment.nodeselector modifier and confirm the CronJob pod template renders nodeSelector.