Release v0.25.0

🚀 Features

• Server-side syntax highlighting for markdown code blocks via
  tartrazine (used by listings before, now everywhere): tz-prefixed
  CSS classes, css/syntax.css with dark/light variants derived from
  the site's color_scheme (or syntax_theme: override); opt out
  with syntax_highlighter: none; highlight.js CDN scripts dropped
  from all bundled themes
• Translation fallback system (#54): untranslated content is rendered
  from its default-language version (or any available translation),
  flagged with is_fallback in the post and page template contexts;
  disable with content_fallback: false in conf.yml
• Site-level language_links helper shared by posts, index pages,
  taxonomy pages and page folder indexes, so translation-switcher
  menus work everywhere (#54)
• Theme parameters: theme.yml's params: section (plus metadata) is
  exposed to all templates as the theme variable; sites override
  values via conf.yml's theme_params: section
• Terminal theme, ported from the Hugo theme by panr (MIT), with
  base16 color-scheme integration and a dark/light toggle
• PaperMod theme, ported from the Hugo theme by adityatelange (MIT),
  with base16 palette and highlight.js token mapping
• Index pages now render with site/theme constants in scope, so
  templates can use site_* and theme.* in index.tmpl
• Theme registry: nicolino theme install/list/remove fetches themes
  from a remote registry (default https://nicolino.ralsina.me/themes.json),
  verifying each tarball's SHA256, so themes can be installed without
  cloning them into the repo by hand
• Root-relative (and url_prefix-aware) link relativization: pages served
  under a subpath now rewrite /css/style.css links to correct relative
  paths, and the link checker resolves .. from nested pages

🐛 Bug Fixes

• Fix remove_empty_paragraphs deleting paragraphs that contain only
  an image (or any element without text), which made markdown images
  disappear from posts whenever the HTML filter pass ran
• Template preprocessor folded {% if %} tags whose body was static
  without checking the condition, silently dropping branches that
  test runtime variables (e.g. is_fallback, language_links)

📚 Documentation

• Theme-porting best practices guide (docs/theme-porting.md)
• Theme showcase site (demo/): markdown tour, code blocks, image,
  i18n with fallback badge, base16 scheme switching