test(generatorConstants): create generatorConstants tests (JhaSourav07#1187)

## Description

Fixes JhaSourav07#1014

Created a new test file for `lib/svg/generatorConstants.ts` covering all
exported constants and helper behavior.

Tests included:

* `SVG_WIDTH === 600`
* `SVG_HEIGHT === 420`
* `FONT_MAP.jetbrains` contains `"JetBrains Mono"`
* `FONT_MAP.fira` contains `"Fira Code"`
* `FONT_MAP.roboto` contains `"Roboto"`
* `isFontKey('jetbrains')` returns `true`
* `isFontKey('roboto')` returns `true`
* `isFontKey('unknown-font')` returns `false`
* `isFontKey('')` returns `false`

## 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.
* [ ] 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/svg/generatorConstants.test.ts

@@ -0,0 +1,40 @@
+import { describe, it, expect } from 'vitest';
+import { SVG_WIDTH, SVG_HEIGHT, FONT_MAP, isFontKey } from './generatorConstants';
+
+describe('generatorConstants', () => {
+  it('SVG_WIDTH equals 600', () => {
+    expect(SVG_WIDTH).toBe(600);
+  });
+
+  it('SVG_HEIGHT equals 420', () => {
+    expect(SVG_HEIGHT).toBe(420);
+  });
+
+  it('FONT_MAP jetbrains contains JetBrains Mono', () => {
+    expect(FONT_MAP.jetbrains).toContain('JetBrains Mono');
+  });
+
+  it('FONT_MAP fira contains Fira Code', () => {
+    expect(FONT_MAP.fira).toContain('Fira Code');
+  });
+
+  it('FONT_MAP roboto contains Roboto', () => {
+    expect(FONT_MAP.roboto).toContain('Roboto');
+  });
+
+  it('isFontKey returns true for jetbrains', () => {
+    expect(isFontKey('jetbrains')).toBe(true);
+  });
+
+  it('isFontKey returns true for roboto', () => {
+    expect(isFontKey('roboto')).toBe(true);
+  });
+
+  it('isFontKey returns false for unknown-font', () => {
+    expect(isFontKey('unknown-font')).toBe(false);
+  });
+
+  it('isFontKey returns false for empty string', () => {
+    expect(isFontKey('')).toBe(false);
+  });
+});