test(CopyRepoButton-timezone-boundaries): verify timezone-boundary co… (JhaSourav07#3222)

## Description

Creates app/components/CopyRepoButton.timezone-boundaries.test.tsx with
5 test cases for CopyRepoButton. Uses vi.useFakeTimers() to control the
2000 ms reset boundary precisely, making tests deterministic across any
system timezone or locale.

Tests:

1. Renders with the default "Copy URL" label regardless of system
timezone
2. Transitions to "Copied!" immediately after a successful clipboard
write
3. Resets to "Copy URL" exactly at the 2000 ms timeout boundary (checks
1999 ms = still "Copied!", 2000 ms = reset)
4. Shows "Copy failed" and resets after 2000 ms when the clipboard API
rejects
5. Writes the exact repo URL to the clipboard, unaffected by locale or
timezone

Fixes JhaSourav07#2810

## 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

## Checklist before requesting a review:

- [x] I have read the `CONTRIBUTING.md` file.
- [x] 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): ...`).
- [x] 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.
- [x] 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

app/components/CopyRepoButton.timezone-boundaries.test.tsx

@@ -0,0 +1,89 @@
+import { cleanup, render, screen, fireEvent, act } from '@testing-library/react';
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest';
+import CopyRepoButton, { REPO_URL } from './CopyRepoButton';
+
+beforeEach(() => {
+  vi.stubGlobal('navigator', {
+    ...navigator,
+    clipboard: { writeText: vi.fn() },
+  });
+});
+
+afterEach(() => {
+  vi.clearAllTimers();
+  vi.useRealTimers();
+  vi.unstubAllGlobals();
+  vi.restoreAllMocks();
+  cleanup();
+});
+
+describe('CopyRepoButton', () => {
+  it('renders with the default "Copy URL" label on mount', () => {
+    render(<CopyRepoButton />);
+    expect(screen.getByRole('button').textContent).toContain('Copy URL');
+  });
+
+  it('transitions to "Copied!" immediately after a successful clipboard write', async () => {
+    vi.useFakeTimers();
+    vi.mocked(navigator.clipboard.writeText).mockResolvedValue(undefined);
+    render(<CopyRepoButton />);
+
+    await act(async () => {
+      fireEvent.click(screen.getByRole('button'));
+    });
+
+    expect(screen.getByRole('button').textContent).toContain('Copied!');
+  });
+
+  it('resets to "Copy URL" exactly after the 2000 ms timeout boundary', async () => {
+    vi.useFakeTimers();
+    vi.mocked(navigator.clipboard.writeText).mockResolvedValue(undefined);
+    render(<CopyRepoButton />);
+
+    await act(async () => {
+      fireEvent.click(screen.getByRole('button'));
+    });
+
+    expect(screen.getByRole('button').textContent).toContain('Copied!');
+
+    await act(async () => {
+      vi.advanceTimersByTime(1999);
+    });
+    expect(screen.getByRole('button').textContent).toContain('Copied!');
+
+    await act(async () => {
+      vi.advanceTimersByTime(1);
+    });
+    expect(screen.getByRole('button').textContent).toContain('Copy URL');
+  });
+
+  it('shows "Copy failed" and resets after 2000 ms when the clipboard API rejects', async () => {
+    vi.useFakeTimers();
+    vi.mocked(navigator.clipboard.writeText).mockRejectedValue(new Error('Not allowed'));
+    render(<CopyRepoButton />);
+
+    await act(async () => {
+      fireEvent.click(screen.getByRole('button'));
+    });
+
+    expect(screen.getByRole('button').textContent).toContain('Copy failed');
+
+    await act(async () => {
+      vi.advanceTimersByTime(2000);
+    });
+    expect(screen.getByRole('button').textContent).toContain('Copy URL');
+  });
+
+  it('writes the exact repo URL exported from the component to the clipboard', async () => {
+    vi.useFakeTimers();
+    vi.mocked(navigator.clipboard.writeText).mockResolvedValue(undefined);
+    render(<CopyRepoButton />);
+
+    await act(async () => {
+      fireEvent.click(screen.getByRole('button'));
+    });
+
+    expect(navigator.clipboard.writeText).toHaveBeenCalledOnce();
+    expect(navigator.clipboard.writeText).toHaveBeenCalledWith(REPO_URL);
+  });
+});

app/components/CopyRepoButton.tsx

@@ -3,14 +3,14 @@
 import { useState } from 'react';
 import { Copy } from 'lucide-react';
 
+export const REPO_URL = 'https://github.com/JhaSourav07/commitpulse';
+
 export default function CopyRepoButton() {
   const [copyState, setCopyState] = useState<'idle' | 'copied' | 'error'>('idle');
 
-  const repoUrl = 'https://github.com/JhaSourav07/commitpulse';
-
   const handleCopy = async () => {
     try {
-      await navigator.clipboard.writeText(repoUrl);
+      await navigator.clipboard.writeText(REPO_URL);
       setCopyState('copied');
     } catch {
       setCopyState('error');