test(i18n): add French badge label coverage (JhaSourav07#3149)

## Description

Fixes JhaSourav07#2337

Adds focused Vitest coverage for French (`fr`) badge label translations
in `lib/i18n/badgeLabels.ts`.

Tests verify:

* The `fr` language key exists in the labels dictionary
* `getLabels('fr')` returns the expected French translations
* Language code casing is handled correctly
* All required translation properties are non-empty strings
* Mock SVG rendering outputs the translated French labels

## Pillar

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

## Visual Preview

Not applicable — test-only change.

## Checklist before requesting a review:

* [x] I have read the `CONTRIBUTING.md` file.
* [ ] 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/i18n/languages/fr.test.ts

@@ -0,0 +1,65 @@
+import { describe, expect, it } from 'vitest';
+import { getLabels, labels } from '../badgeLabels';
+
+const requiredKeys = [
+  'CURRENT_STREAK',
+  'ANNUAL_SYNC_TOTAL',
+  'PEAK_STREAK',
+  'COMMITS_THIS_MONTH',
+  'VS_LAST_MONTH',
+] as const;
+
+const expectedFrenchLabels = {
+  CURRENT_STREAK: 'SÉRIE_ACTUELLE',
+  ANNUAL_SYNC_TOTAL: 'TOTAL_ANNUEL',
+  PEAK_STREAK: 'SÉRIE_MAXIMALE',
+  COMMITS_THIS_MONTH: 'COMMITS CE MOIS',
+  VS_LAST_MONTH: 'vs mois dernier',
+};
+
+function renderMockBadge(lang: string) {
+  const badgeLabels = getLabels(lang);
+
+  return `
+    <svg role="img" data-lang="${lang}">
+      <text>${badgeLabels.CURRENT_STREAK}</text>
+      <text>${badgeLabels.ANNUAL_SYNC_TOTAL}</text>
+      <text>${badgeLabels.PEAK_STREAK}</text>
+      <text>${badgeLabels.COMMITS_THIS_MONTH}</text>
+      <text>${badgeLabels.VS_LAST_MONTH}</text>
+    </svg>
+  `;
+}
+
+describe('French badge labels', () => {
+  it('includes the fr language key in the labels dictionary', () => {
+    expect(labels.fr).toBeDefined();
+  });
+
+  it('returns the exact French translation mapping through getLabels', () => {
+    expect(getLabels('fr')).toEqual(expectedFrenchLabels);
+  });
+
+  it('returns the French mapping when lang code casing differs', () => {
+    expect(getLabels('FR')).toEqual(expectedFrenchLabels);
+  });
+
+  it('sets every required French label to a non-empty string', () => {
+    const frenchLabels = getLabels('fr');
+
+    for (const key of requiredKeys) {
+      expect(typeof frenchLabels[key]).toBe('string');
+      expect(frenchLabels[key].trim().length).toBeGreaterThan(0);
+    }
+  });
+
+  it('renders a mock SVG with French translated labels', () => {
+    const svg = renderMockBadge('fr');
+
+    expect(svg).toContain('data-lang="fr"');
+
+    for (const value of Object.values(expectedFrenchLabels)) {
+      expect(svg).toContain(value);
+    }
+  });
+});