feat: support additional_tags on worker launch template

[lorenzstorm1]

Summary

Adds an additional_tags field to runner_worker_docker_autoscaler_instance that applies tags exclusively to the worker launch template's tag_specifications (instance, volume, network-interface) without affecting the runner manager instance.

This enables use cases like excluding ephemeral CI workers from AWS GuardDuty Runtime Monitoring while keeping the manager monitored.

Usage

runner_worker_docker_autoscaler_instance = {
  additional_tags = { "GuardDutyManaged" = "false" }
}

Closes #1369

Changes

• variables.tf: Add additional_tags = optional(map(string), {}) to the runner_worker_docker_autoscaler_instance object
• tags.tf: Add worker_tags local that merges local.tags with the new additional_tags
• docker_autoscaler.tf: Use local.worker_tags in tag_specifications blocks

🤖 Generated with Claude Code

[github-actions]

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