[rogeraabbccdd]

Main target of this pull request is improving SEO using an AI agent,
Search engines should index one URL per page in every language, and see each page's real content.

Part 1 - Indexing

• Canonical and hreflang links on every page
• Redirect every page to a single URL (locale, trailing slash, http)
• Answer unknown URLs and deleted patterns, skins, setlists and users with a real 404
• Only list profile tabs with content in sitemap.xml
• Redirect logged-out form pages instead of rendering the home page

Part 2 - Content

• Render the pattern, skin and setlist lists on the server
• Render descriptions on the server
• Structured data on the home and detail pages
• One h1 per page
• Fix og:image and the fallback header images
• Rewrite page titles and descriptions

Part 3 - i18n

• Fix mistranslated and untranslated strings
• Use the game's terms
• Translate the 404 page

Part 4 - Others

• Let users zoom the page on mobile
• Fix hydration mismatches and keep sanitize-html out of the client bundle
• Redirect the old GitHub Pages domain with meta refresh and canonical