feat: Add WCAG accessibility audit automation

Description

Automate accessibility testing by integrating axe-core or Lighthouse CI into the GitHub Actions workflow.

Problem

• No automated accessibility testing
• Manual testing is time-consuming and inconsistent
• WCAG compliance not verified
• Accessibility regressions can go unnoticed

Current Accessibility Features

• prefers-reduced-motion support in animations
• Semantic HTML structure
• No automated testing

Proposed Solution

Add automated a11y testing with:

• axe-core - Fast, comprehensive accessibility testing
• Lighthouse CI - Full accessibility audit
• Run on every PR
• Fail CI if critical issues found

Implementation Options

Option 1: axe-core with Playwright

import { test, expect } from '@playwright/test';
import AxeBuilder from '@axe-core/playwright';

test('Homepage should not have accessibility violations', async ({ page }) => {
  await page.goto('/');
  const results = await new AxeBuilder({ page }).analyze();
  expect(results.violations).toEqual([]);
});

Option 2: Lighthouse CI

- name: Run Lighthouse CI
  uses: treosh/lighthouse-ci-action@v10
  with:
    urls: |
      http://localhost:3000
      http://localhost:3000/quizzes
    configPath: './.lighthouserc.json'

Acceptance Criteria

• Install axe-core or Lighthouse CI
• Add accessibility tests for key pages
• Test: Homepage
• Test: Quizzes page
• Test: Quiz detail page
• Test: Post page
• Test: Games page
• Configure GitHub Actions workflow
• Fail builds on critical violations
• Generate accessibility report
• Document how to fix common issues

Files to Create/Modify

• .github/workflows/accessibility.yml - New workflow
• .lighthouserc.json - Lighthouse config (if using Lighthouse)
• tests/accessibility/*.test.ts - Accessibility tests
• docs/accessibility.md - Documentation