test(generateMonthlySVG): verify custom width and height appear in SVG viewBox (JhaSourav07#1172)

Fixes JhaSourav07#1050

## Description

Added a test to verify that `generateMonthlySVG` correctly reflects
custom `width` and `height` values in the SVG `viewBox`.

## Pillar

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

## Visual Preview

N/A (test-only change)

## Checklist before requesting a review:

* [x] I have read the `CONTRIBUTING.md` file.
* [x] I have tested these changes locally (`npm test
lib/svg/generator.test.ts`).
* [x] I have run `npm run format` and `npm run lint` locally and
resolved all errors (CI will verify).
* [x] My commits follow the Conventional Commits format.
* [ ] I have updated `README.md` if I added a new theme or URL
parameter. (Not applicable)
* [x] I have starred the repo.
* [x] I have made sure that I have only one commit to merge in this PR.
* [x] The SVG output matches the CommitPulse quality standards.
* [x] I joined the CommitPulse Discord community.

Author: svasidhar

lib/svg/generator.test.ts

@@ -745,6 +745,16 @@ describe('generateMonthlySVG', () => {
     expect(svg).toContain('+40% (+12)');
   });
 
+  it('includes custom dimensions in viewBox', () => {
+    const svg = generateMonthlySVG(mockMonthlyStats, {
+      user: 'octocat',
+      width: 400,
+      height: 200,
+    } as unknown as BadgeParams);
+
+    expect(svg).toContain('viewBox="0 0 400 200"');
+  });
+
   it('respects custom width and height parameters', () => {
     const svg = generateMonthlySVG(mockMonthlyStats, {
       user: 'octocat',