Improve error handling in create-labels workflow

[Copilot]

Description

Enhanced error handling in the create-labels.yaml workflow to distinguish between expected label-already-exists scenarios and actual failures (authentication, rate limiting, API errors).

Changes:

• Check error status 422 and already_exists code before ignoring
• Log informational messages when labels exist
• Re-throw non-duplicate errors to surface real issues

Before:

catch (error) {
  // Ignore if label already exists
}

After:

catch (error) {
  if (error.status === 422 && error.response?.data?.errors?.[0]?.code === 'already_exists') {
    console.log('Label "dependabot - security" already exists, skipping creation');
  } else {
    console.error('Failed to create label "dependabot - security":', error.message);
    throw error;
  }
}

Type of change

• Bug fix
• New feature
• Breaking change
• Documentation update
• Refactor

How Has This Been Tested?

• YAML syntax validation
• Error handling logic review
• Workflow structure verification

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

Screenshots (if applicable)

N/A - GitHub Actions workflow change

Additional context

Addresses feedback from PR #27 review comment about silent error handling masking real issues.

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