test(calculateStreak): add full year zero contributions edge case test (JhaSourav07#1715)

## Description

Fixes JhaSourav07#1483 

## Pillar

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

## Visual Preview

## Checklist before requesting a review:

- [x] I have read the `CONTRIBUTING.md` file.
- [x] I have tested these changes locally
(`localhost:3000/api/streak?user=YOUR_USERNAME`).
- [x] I have run `npm run format` and `npm run lint` locally and
resolved all errors (CI will fail otherwise).
- [x] 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.
- [x] I have started the repo.
- [x] 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).
- [x] (Recommended) I joined the CommitPulse Discord community for
contributor discussions, mentorship, and faster PR support.

Author: JhaSourav07

lib/calculate.test.ts

@@ -1352,6 +1352,20 @@ describe('calculateStreak — empty and sparse year edge cases', () => {
     expect(result.todayDate).toBeDefined();
   });
 
+  it('returns all zeros for an entire year (52 weeks × 7 days) of empty contributions (Variation 5)', () => {
+    // 52 weeks × 7 days = 364 days, every day has 0 commits.
+    const emptyYearCounts = Array(364).fill(0);
+    const calendar = buildCalendar(emptyYearCounts);
+
+    const fixedNow = new Date('2024-01-15T12:00:00Z');
+    const result = calculateStreak(calendar, 'UTC', fixedNow);
+
+    expect(result.currentStreak).toBe(0);
+    expect(result.longestStreak).toBe(0);
+    expect(result.totalContributions).toBe(0);
+    expect(result.todayDate).toMatch(/^\d{4}-\d{2}-\d{2}$/);
+  });
+
   it('is deterministic: same empty calendar always returns identical output', () => {
     const calendar = buildCalendar([]);
     const fixedNow = new Date('2024-01-15T12:00:00Z');