test(utils): add boundary robustness tests for time normalization (#1549)

[YerraguntaAjayKumar]

Description

This PR introduces boundary robustness tests for time and date range normalization utilities. Specifically, it ensures correct calculation of seconds until midnight across extreme timezones (e.g., UTC-12, UTC+14) without accidental calendar shifting, and verifies sliding window boundary TTLs. It also adds tests to validate safe fallbacks when partial or omitted date ranges are passed.

Fixes #1549

Pillar

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

Visual Preview

N/A - Back-end test suite additions only.

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.
• 1 new test block added for this utility function.
• 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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[github-actions]

⚠️ Hey @YerraguntaAjayKumar, this PR has merge conflicts with the main branch.

Please pull the latest changes and resolve the conflicts so we can review it!

git fetch origin
git rebase origin/main
# resolve any conflicts, then:
git push --force-with-lease

Once resolved, the needs-rebase label will be removed automatically on the next check. 🙌

[github-actions]

⚠️ Hey @YerraguntaAjayKumar, this PR has merge conflicts with the main branch.

Please pull the latest changes and resolve the conflicts so we can review it!

git fetch origin
git rebase origin/main
# resolve any conflicts, then:
git push --force-with-lease

Once resolved, the needs-rebase label will be removed automatically on the next check. 🙌

[github-actions]

🚨 Hey @YerraguntaAjayKumar, the CI Pipeline is failing on this PR and it has been marked as status:blocked.

Please fix the issues before this can be reviewed. Here's how:

1. Run checks locally before pushing:

npm run format:check   # Check Prettier formatting
npm run lint           # Run ESLint
npm run typecheck      # TypeScript type check
npm run test           # Run unit tests (Vitest)
npm run build          # Verify production build passes

2. Auto-fix common issues:

npm run format         # Auto-fix formatting with Prettier
npm run lint -- --fix  # Auto-fix lint errors where possible

3. Check the full failure log here:
👉 View CI Run

Once you push a fix and the CI passes, the status:blocked label will be removed automatically. 💪

[YerraguntaAjayKumar]

Hey! Just wanted to let you know I've resolved the merge conflicts and fixed the formatting/syntax issues. The CI pipeline is now fully passing and everything is synced up with main. It should be good to go for review whenever you have time. Thank you!

[Aamod007]

Adds 2 timezone boundary tests for extreme offsets: UTC-12 (10 seconds to midnight) and UTC+12/UTC-14 (full 86400s at local midnight). Also adds Arrange/Act/Assert comments to existing date range validation tests. Clean +46/-0, all tests pass.