docs: align Renovate maintenance config

Summary

Align Renovate-generated labels with Package Maintenance and apply the shared post-upgrade tasks to every Docker/Helm update grouped on the Ironbank branch.

Validation

• jq empty renovate.json
• CI-pinned Renovate 42.0.1 full dry run on 168-renovate-maintenance-config
• Docker and Helm updates resolved to one grouped branch; bump-chart-bb-suffix, changelog, and docs tasks each executed once; the chart retained the upstream version base with -bb.0

Linked issues

Closes #168 (closed)

Upgrade Notices

None.