test(contributors-loading): add loading component test coverage (JhaSourav07#3109)

## Description

Adds a test suite for the contributors loading fallback component.

## Tests Added

- Renders loading fallback successfully
- Displays loading messages
- Verifies animated loader classes
- Validates centered layout and themed backdrop
- Confirms accessibility attributes

Fixes JhaSourav07#2288 

## Pillar

- [x] 📐 Pillar 2 — Geometric SVG Improvement
- [x] 🛠️ Other (Bug fix, refactoring, docs)


## 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/contributors/loading.test.tsx

@@ -0,0 +1,48 @@
+import { render, screen } from '@testing-library/react';
+import '@testing-library/jest-dom/vitest';
+import { describe, it, expect } from 'vitest';
+import Loading from './loading';
+
+describe('Contributors Loading', () => {
+  it('renders loading fallback component', () => {
+    render(<Loading />);
+
+    expect(screen.getByRole('status')).toBeInTheDocument();
+  });
+
+  it('renders loading messages correctly', () => {
+    render(<Loading />);
+
+    expect(screen.getByText(/loading the collective/i)).toBeInTheDocument();
+
+    expect(screen.getByText(/fetching contributor data from github/i)).toBeInTheDocument();
+  });
+
+  it('contains animated loader elements', () => {
+    const { container } = render(<Loading />);
+
+    expect(container.querySelector('.animate-spin')).toBeInTheDocument();
+
+    expect(container.querySelector('.animate-pulse')).toBeInTheDocument();
+  });
+
+  it('maintains centered flex layout and themed backdrop', () => {
+    const { container } = render(<Loading />);
+
+    const wrapper = container.firstChild as HTMLElement;
+
+    expect(wrapper).toHaveClass('flex');
+    expect(wrapper).toHaveClass('min-h-screen');
+    expect(wrapper).toHaveClass('items-center');
+    expect(wrapper).toHaveClass('justify-center');
+    expect(wrapper).toHaveClass('bg-[#050505]');
+  });
+
+  it('renders loader container with accessibility attributes', () => {
+    render(<Loading />);
+
+    const status = screen.getByRole('status');
+
+    expect(status).toHaveAttribute('aria-live', 'polite');
+  });
+});