test: Add unit test for `GithubLink` component

[O2sa]

Add a simple unit test for the GithubLink component to verify it renders correctly and contains the correct href and aria-label. This is a small, approachable test for new contributors.

Tasks

• Create a test file test/ui/github-link.test.tsx (or similar) using the existing test framework (vitest + testing-library).
• Render GithubLink and assert the anchor's href and aria-label are present.
• Run the test suite and ensure it passes.

Tip

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