test: add theme contrast tests for RepoPerformanceTable

[gamana618]

• Add 5 test cases for dark/light mode visual cohesion
• Verify Tailwind classes for both themes
• Ensure table content accessibility
• Closes test(RepoPerformanceTable-theme-contrast): verify Dark and Light Prefers-Color-Scheme Visual Cohesion (Variation 3) #4489

Description

Fixes #4489

Pillar

• 🎨 Pillar 1 — New Theme Design
• 📐 Pillar 2 — Geometric SVG Improvement
• 🕐 Pillar 3 — Timezone Logic Optimization
• 🛠️ Other (Bug fix, refactoring, docs)

Visual Preview

Checklist before requesting a review:

• I have read the CONTRIBUTING.md file.
• I have tested these changes locally (localhost:3000/api/streak?user=YOUR_USERNAME).
• I have run npm run format and npm run lint locally and resolved all errors (CI will fail otherwise).
• My commits follow the Conventional Commits format (e.g., feat(themes): ..., fix(calculate): ...).
• I have updated README.md if I added a new theme or URL parameter.
• I have started the repo.
• I have made sure that i have only one commit to merge in this PR.
• The SVG output matches the CommitPulse "premium quality" aesthetic standard (no raw elements, smooth animations, correct fonts).
• (Recommended) I joined the CommitPulse Discord community for contributor discussions, mentorship, and faster PR support.

[vercel]

@gamana618 is attempting to deploy a commit to the jhasourav07's projects Team on Vercel.

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[Aamod-Dev]

Thanks for the contribution. I went through the changes and the overall approach looks good.

[github-actions]

🎉 Congratulations @gamana618! Your PR has been successfully merged. 🚀

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