Add Nuxt frontend with blog index, article and category pages

The browser never talks to Strapi: pages call Nitro endpoints under
server/api/, which are the only place Strapi queries are built. That keeps the
Strapi URL internal to the Docker network and avoids CORS entirely.

Article bodies are rendered from Markdown to HTML in the endpoint, so the
content is server-rendered and crawlable, marked stays out of the client
bundle, and the meta description is derived from the opening of the body.

Pages carry canonical URLs, Open Graph tags and BlogPosting structured data,
and handle empty, missing and failed states.

frontend/.dockerignore

@@ -0,0 +1,6 @@
+node_modules
+.nuxt
+.output
+.data
+.env
+.git