style(test): format sanitizeFont tests (JhaSourav07#609)

## Description

Fixes JhaSourav07#343

Expanded test coverage for `sanitizeFont` in
`lib/svg/sanitizer.test.ts`.

### Added edge case tests

* null input returns null
* whitespace-only input returns null
* valid font names with spaces are preserved
* numeric font names are allowed
* script injection attempts are sanitized
* invalid characters that sanitize to empty return null

## Pillar

* [x] 🛠️ Other (Bug fix, refactoring, docs)

## Visual Preview

N/A (test-only changes)

## Checklist before requesting a review:

* [x] I have read the `CONTRIBUTING.md` file.
* [x] I have tested these changes locally.
* [x] I have run `npm run format` and `npm run lint` locally and
resolved all errors.
* [x] My commits follow the Conventional Commits format.
* [ ] I have updated `README.md` if needed.
* [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 (not applicable).
* [ ] (Recommended) I joined the CommitPulse Discord community.

Close JhaSourav07#343

Author: JhaSourav07

lib/svg/sanitizer.test.ts

@@ -97,6 +97,30 @@ describe('SVG Sanitizer Utilities', () => {
     it('returns null for completely invalid font', () => {
       expect(sanitizeFont('!!!')).toBe(null);
     });
+
+    it('returns null for null input', () => {
+      expect(sanitizeFont(null)).toBe(null);
+    });
+
+    it('returns null for whitespace-only input', () => {
+      expect(sanitizeFont('   ')).toBe(null);
+    });
+
+    it('preserves valid font names with spaces', () => {
+      expect(sanitizeFont('Fira Code')).toBe('Fira Code');
+    });
+
+    it('allows numeric font names', () => {
+      expect(sanitizeFont('123')).toBe('123');
+    });
+
+    it('sanitizes script injection attempts', () => {
+      expect(sanitizeFont('<script>alert(1)</script>')).toBe('scriptalert1script');
+    });
+
+    it('returns null when sanitization removes all characters', () => {
+      expect(sanitizeFont('@@@')).toBe(null);
+    });
   });
 
   describe('sanitizeGoogleFontUrl', () => {