Add AUR package update trigger to release workflow

[bpauli]

Summary

• Add update-aur job to the release workflow, parallel to the existing update-homebrew job
• On release, triggers the update-package.yml workflow in bpauli/aur-packages to update the gccli-bin AUR package
• Supports both tag-push and manual workflow_dispatch triggers

Test plan

• Verify the workflow YAML is valid
• Trigger a test release and confirm both update-homebrew and update-aur jobs run successfully