Improve SEO

[htorresUVa]

Summary

Improves SEO and social sharing for codi.link by adding metadata, structured data, favicons/manifest, a sitemap/robots.txt, and a proper semantic heading.

• Added canonical URL, robots meta and author meta tags to index.html
• Added Open Graph (og:*, including og:locale) and Twitter Card meta tags for rich link previews, backed by a new public/og-image.png
• Added WebApplication JSON-LD structured data for search engines
• Added public/robots.txt and public/sitemap.xml to improve crawlability and indexing
• Added a visually hidden <h1> (.sr-only) so the page has a proper semantic heading without changing the visual design
• Added a full favicon set (SVG, 32x32 PNG, Apple touch icon) and a site.webmanifest for PWA/home-screen support
• Added theme-color meta tag to match the app's dark UI

Why

The site had no <h1>, no meta description/OG tags, no robots.txt/sitemap.xml, and only a single .ico favicon — this hurt search indexing, produced blank/broken previews when shared on social media, and gave a poor "add to home screen" experience.

Changes

File	Change
index.html	Canonical link, robots/author/theme-color meta, favicon set, manifest link, OG + Twitter meta tags, JSON-LD, hidden <h1>
public/og-image.png	New Open Graph image (1512x950)
public/robots.txt	New file, allows all crawlers, points to sitemap
public/sitemap.xml	New sitemap listing the homepage
public/site.webmanifest	New web app manifest (name, colors, icons)
public/assets/midu.svg, favicon-32x32.png, apple-touch-icon.png	New favicon/branding assets
src/css/base.css	New .sr-only utility class for the hidden heading

Testing

• Verified page still renders and behaves identically (heading is visually hidden)
• Validated Open Graph tags with a link-preview debugger (Twitter/Facebook)
• Validated sitemap.xml / robots.txt are served correctly at /sitemap.xml and /robots.txt
• Verified favicons render correctly across browsers and site.webmanifest is picked up (Lighthouse/PWA check)

Checklist

• I have authored 100% of this content
• I have the necessary rights to the content contributed
• I agree this contribution is provided under the project's license