feat: Add canonical URL audit and consistency check

Description

Audit all pages for proper canonical URL tags and ensure consistency across the site to prevent duplicate content SEO issues.

Problem

• Canonical URLs may not be set on all pages
• Risk of duplicate content penalties
• Inconsistent URL patterns across site
• No automated verification of canonical tags

SEO Impact

• Search engines may index wrong version of pages
• Duplicate content dilutes page authority
• Could affect search rankings
• Wasted crawl budget

Pages to Audit

Content Pages

• Posts: /posts/[slug]
• Guides: /guides/[slug] and /guides/[slug]/[part]
• Quizzes: /quizzes/[slug]
• Games: /games/[slug]
• News: /news/[slug]
• Exercises: /exercises/[id]

Listing Pages

• Homepage: /
• Posts index: /posts
• Guides index: /guides
• Quizzes index: /quizzes
• Games index: /games
• Tags: /tags/[tag]
• Categories: /categories/[slug]
• Authors: /authors/[slug]

Paginated Pages

• Check if pagination exists
• Ensure proper canonical for paginated results

Current State Check

# Search for canonical tags
rg '<link rel="canonical"' app/

# Check metadata generation
cat app/*/page.tsx | grep canonical

Proposed Solution

1. Audit existing canonical tags
2. Add canonical to all page metadata
3. Create utility function for canonical URLs
4. Add automated tests

Implementation Example

// lib/canonical.ts
export function getCanonicalUrl(path: string): string {
  const baseUrl = 'https://devops-daily.com';
  return `${baseUrl}${path}`;
}

// In page.tsx
export const metadata: Metadata = {
  title: 'Post Title',
  alternates: {
    canonical: getCanonicalUrl('/posts/my-post')
  }
};

Acceptance Criteria

• Audit all pages for canonical tags
• Create canonical URL utility function
• Add canonical to all page metadata
• Ensure consistent URL patterns (trailing slashes, etc.)
• Add automated test for canonical tags
• Verify in production with view-source
• Add to SEO checklist
• Document canonical URL conventions

Testing

// tests/canonical-urls.test.ts
import { describe, it, expect } from 'vitest';
import { getCanonicalUrl } from '@/lib/canonical';

describe('Canonical URLs', () => {
  it('generates correct canonical URL', () => {
    expect(getCanonicalUrl('/posts/test')).toBe(
      'https://devops-daily.com/posts/test'
    );
  });

  it('handles trailing slashes', () => {
    expect(getCanonicalUrl('/posts/test/')).toBe(
      'https://devops-daily.com/posts/test'
    );
  });
});

Files to Create/Modify

• lib/canonical.ts - New utility
• tests/canonical-urls.test.ts - New tests
• All page.tsx files - Add canonical metadata
• docs/seo.md - Document canonical URL strategy