feat: public API, SEO and existing surfaces

docs/llm/recipe-articles.md

@@ -79,3 +79,14 @@ curl "{{BASE_URL}}/v1/article/1?format=markdown"
 ```
 
 Before step 4 this answers `404` with the text `Article not found`, because anonymous callers only see online articles.
+
+## Read a language version (public)
+
+Two public routes, no credential needed (a cookie or key is ignored and a draft is never returned):
+
+```
+GET /v1/public/site/journal/lang/fr/article/comment-nous-chiffrons-une-renovation
+GET /v1/public/site/journal/story/5?lang=fr&fallback=default
+```
+
+The first matches site, language and slug exactly and never falls back (`404 article_not_found`). The second resolves a story: without `lang` it asks for the site default language, and `fallback=default` serves the default-language version when the requested one is not published (`fallback: true`, `requested_lang` keeps the asked language); otherwise `404 language_not_available`. Both answer the article object plus `alternates`, the other published versions of the story in enabled languages (`id`, `lang`, `story_id`, `slug`, `url`; `url` is `null` when the site has no Public URL pattern), default language first, then by tag. An invalid `lang` is `400 invalid_language`.