fix(accordion): enforce top border for all accordions

[hugomslv]

📄 Description

Made sure even a single accordion item always shows a top border.

🚀 Demo

If applicable, please add a screenshot or video to illustrate the changes.

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📝 Checklist

• ✅ My code follows the style guidelines of this project
• 🛠️ I have performed a self-review of my own code
• 📄 I have made corresponding changes to the documentation
• ⚠️ My changes generate no new warnings or errors
• 🧪 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

[changeset-bot]

🦋 Changeset detected

Latest commit: 36938b6

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 12 packages

Name	Type
@swisspost/design-system-components	Patch
@swisspost/design-system-components-angular-workspace	Patch
@swisspost/design-system-components-react	Patch
@swisspost/design-system-documentation	Patch
@swisspost/design-system-components-angular	Patch
@swisspost/design-system-nextjs-integration	Patch
@swisspost/design-system-styles	Patch
@swisspost/design-system-tokens	Patch
@swisspost/design-system-icons	Patch
@swisspost/design-system-styles-primeng	Patch
@swisspost/internet-header	Patch
@swisspost/design-system-styles-primeng-workspace	Patch

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[swisspost-bot]

Related Previews

• https://preview-6151--swisspost-design-system-next.netlify.app

[sonarqubecloud]

Quality Gate failed

Failed conditions
1 New Code Smells (required ≤ 0)

See analysis details on SonarQube Cloud

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[leagrdv]

You have a sonar error and tests are not passing, could you fix it?