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.