[InputFile] [a11y] Fix missing focus indicator in FluentInputFile (#3693)

[MarvinKlein1508]

Pull Request

📖 Description

This PR fixes the missing focus indicator in FluentInputFile.

Before:

After:

🎫 Issues

Fixes #3693

👩‍💻 Reviewer Notes

This issue is being caused by the input field having opacity set to 0. This results in the UI not showing any focus borders. This PR fixes this by giving the parent container the corresponding outline.

📑 Test Plan

✅ Checklist

General

• I have added tests for my changes.
• I have tested my changes.
• I have updated the project documentation to reflect my changes.
• I have read the CONTRIBUTING documentation and followed the standards for this project.

Component-specific

• I have added a new component
• I have added Unit Tests for my new component
• I have modified an existing component
• I have validated the Unit Tests for an existing component