fix: Fix corner radius handling on Wasm

[Youssef1313]

GitHub Issue (If applicable): Wasm part of #10263

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Copilot Summary

🤖 Generated by Copilot at 17282ef

This pull request improves the border rendering of various UI elements on the WASM platform, by adding support for rounded corners based on the CornerRadius property and updating the border layer with the correct properties when they change. It also fixes a typo in a sample and simplifies the API for setting the border layer in the FrameworkElement class.

PR Checklist

Please check if your PR fulfills the following requirements:

• Docs have been added/updated which fit documentation template (for bug fixes / features)
• Unit Tests and/or UI Tests for the changes have been added (for bug fixes / features) (if applicable)
• Validated PR Screenshots Compare Test Run results.
• Contains NO breaking changes
• Associated with an issue (GitHub or internal) and uses the automatic close keywords.
• Commits must be following the Conventional Commits specification.

Other information

Internal Issue (If applicable):

[MartinZikmund]

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