test: add explicit timeout to massive scaling background refresh test

[kanishka-2007-tech]

Description

This PR addresses flaky CI builds caused by timeout issues in the massive scaling test suite.
The test entitled "maintains correctness across 10 sequential massive cycles of 10k triggers each" generates and validates 100,000 operations. Due to the O(n) or O(n^2) nature of these massive loops, the execution time can vary and occasionally exceed standard limits, causing intermittent failures.

Changes Made

• services/github/background-refresh.massive-scaling.test.ts:
  • Appended an explicit timeout parameter of 15000 (15 seconds) to the massive sequential test block.
  • Converted the test callback to an async function to properly accommodate the timeout boundaries and align with modern asynchronous test patterns.

Fixes #3673

Pillar

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

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.

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[retenta-bot]

This PR addresses the flaky CI builds by introducing a timeout to the massive scaling test, which is crucial for maintaining test reliability. Similar past decisions have focused on enhancing test coverage and resilience, such as adding tests for timezone normalization and error handling in utility functions. These efforts collectively aim to improve the robustness of our testing framework. Thank you for your contribution!

[github-actions]

📦 Next.js Bundle Size Report (Gzipped Sizes)

✨ No significant bundle size changes detected.

📊 Summary of Totals

Category	PR Size	Base Size	Difference
Total JS	3975.85 KB	3975.85 KB	0 B
Total CSS	331.16 KB	331.16 KB	0 B