test(copyrepobutton): add theme contrast coverage (JhaSourav07#3028)

## Description

Fixes JhaSourav07#2805

Added theme contrast test coverage for
`app/components/CopyRepoButton.tsx`.

### Tests Added

* Verifies light mode background and border contrast classes.
* Verifies dark mode background and border contrast classes.
* Ensures readable font weight is preserved.
* Confirms icon and text spacing classes prevent overlap.
* Verifies transition and hover classes do not remove contrast styling.

## 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 changes)

## Checklist before requesting a review:

* [x] I have read the `CONTRIBUTING.md` file.
* [x] I have tested these changes locally.
* [ ] 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 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.
* [ ] The SVG output matches the CommitPulse "premium quality" aesthetic
standard. (Not applicable)
* [ ] (Recommended) I joined the CommitPulse Discord community.

Author: JhaSourav07

app/components/CopyRepoButton.theme-contrast.test.tsx

@@ -0,0 +1,55 @@
+import { render, screen } from '@testing-library/react';
+import { describe, expect, it, vi } from 'vitest';
+
+import CopyRepoButton from './CopyRepoButton';
+
+vi.mock('lucide-react', () => ({
+  Copy: () => <svg data-testid="copy-icon" />,
+}));
+
+describe('CopyRepoButton theme contrast behavior', () => {
+  it('includes light mode background and border contrast classes', () => {
+    render(<CopyRepoButton />);
+
+    const button = screen.getByRole('button', { name: /copy url/i });
+
+    expect(button.className).toContain('bg-white/60');
+    expect(button.className).toContain('border-black/10');
+  });
+
+  it('includes dark mode background and border contrast classes', () => {
+    render(<CopyRepoButton />);
+
+    const button = screen.getByRole('button', { name: /copy url/i });
+
+    expect(button.className).toContain('dark:bg-white/5');
+    expect(button.className).toContain('dark:border-white/10');
+  });
+
+  it('keeps readable font weight for button text', () => {
+    render(<CopyRepoButton />);
+
+    expect(screen.getByRole('button').className).toContain('font-semibold');
+  });
+
+  it('preserves spacing classes so icon and text do not overlap', () => {
+    render(<CopyRepoButton />);
+
+    const button = screen.getByRole('button');
+
+    expect(button.className).toContain('inline-flex');
+    expect(button.className).toContain('items-center');
+    expect(button.className).toContain('gap-2');
+  });
+
+  it('keeps transition and hover classes without removing contrast styling', () => {
+    render(<CopyRepoButton />);
+
+    const button = screen.getByRole('button');
+
+    expect(button.className).toContain('transition-all');
+    expect(button.className).toContain('hover:scale-105');
+    expect(button.className).toContain('bg-white/60');
+    expect(button.className).toContain('dark:bg-white/5');
+  });
+});