Refactor auth config to eliminate duplication

[hjensas]

Move auth_url into auth_config template definitions and consolidate auth config across templates.

Changes:

• Add auth_url to auth_config template in common/ironic.conf, inspector, and neutron-agent configs
• Remove duplicate auth_url lines across all templates
• Add [ironic] section to common config for API client authentication
• Remove duplicate auth sections from ironicapi/01-api.conf
• Update ironicapi test to check ironic.conf for auth configuration

Assisted-By: Claude Code/claude-4.5-sonnet

Checklist before requesting a review

• I have performed a self-review of my code and confirmed it passes tests
• Performed pre-commit run --all
• Tested operator image in a test/dev environment. It can be CRC via install_yamls or a hotstack instance (optional)
• Verified that no failures present in logs(optional):
  • ironic-operator-build-deploy-kuttl
  • podified-multinode-ironic-deployment

[softwarefactory-project-zuul]

Build failed (check pipeline). Post recheck (without leading slash)
to rerun all jobs. Make sure the failure cause has been resolved before
you rerun jobs.

https://softwarefactory-project.io/zuul/t/rdoproject.org/buildset/ca2039b0aa174f0984870e8e16081fc5

❌ openstack-k8s-operators-content-provider FAILURE in 13m 23s
⚠️ podified-multinode-ironic-deployment SKIPPED Skipped due to failed job openstack-k8s-operators-content-provider

[steveb]

Looks good. Job failure was due to not being able to pull docker://registry.access.redhat.com/ubi9/ubi-minimal:9.6 so not related

[openshift-ci]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: hjensas, steveb

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[hjensas]

recheck