test(streak route): verify SVG viewBox output

[mayank200529]

Description

Fixes #699

Added assertions to verify that the SVG response generated by the streak route contains:

• viewBox attribute for proper SVG scaling
• xmlns="http://www.w3.org/2000/svg" namespace declaration

This helps ensure generated badges remain valid SVGs and scale correctly in GitHub READMEs and other embedding contexts.

Pillar

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

Visual Preview

Not applicable — test-only change.

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]

@mayank200529 is attempting to deploy a commit to the jhasourav07's projects Team on Vercel.

A member of the Team first needs to authorize it.

[mayank200529]

@JhaSourav07 please check the authorization of vecel part

[github-actions]

🎉 Congratulations @mayank200529! Your PR has been successfully merged. 🚀

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