- Slugify tag/category static params so pre-rendered pages match links;
disable dynamic params and return a real 404 via notFound()
- Drop bogus generateStaticParams from the tags/categories index pages
- Add a styled not-found page
- Sort 'Recently updated' by last modification before slicing
- Atom feed: correct rel=self URL, use updated dates, valid content type
- Swap no-js -> js class in an inline head script before first paint
- Markdown links: only route internal paths through next/link and
tolerate missing hrefs
