Add hand-rolled English support (/en/*) alongside the Italian site

PocketBase gains optional, manually-authored English fields on articles
and categories (same record, same slug), and the frontend serves an /en
counterpart of every dynamic route via thin page wrappers around shared
view components — no i18n library, consistent with the project's existing
minimalism stance for a two-locale site with ~20 UI strings.

An article/category with no translation 404s cleanly on its own /en
detail page and is filtered out of /en listings, and the header's
language-switch link falls back to the English blog index rather than a
dead link; resolving that requires a global route middleware, since the
layout's header renders before the page content in document order and so
can't react to state a page component sets during its own async setup.

frontend/app/middleware/lang-switch.global.ts

@@ -0,0 +1,47 @@
+import type { Article, Category } from '#shared/types/blog'
+
+/**
+ * Resolves the language-switch target *before* the layout (and its header,
+ * rendered ahead of the page in document order) mounts — setting this from
+ * inside the page component itself is too late: a parent renders its
+ * children in document order, so the header's LanguageSwitch would already
+ * be resolved before the page's own setup ever runs, translated content or
+ * not. Running as global route middleware guarantees this resolves first.
+ */
+export default defineNuxtRouteMiddleware(async (to) => {
+  const langSwitch = useLangSwitchState()
+  const locale = to.path === '/en' || to.path.startsWith('/en/') ? 'en' : 'it'
+  const bare = locale === 'en' ? to.path.slice(3) || '/' : to.path
+
+  const articleMatch = bare.match(/^\/blog\/([^/]+)$/)
+  const categoryMatch = bare.match(/^\/category\/([^/]+)$/)
+
+  if (articleMatch) {
+    const slug = articleMatch[1]
+    const { data } = await useFetch<Article>(`/content/articles/${slug}`, {
+      key: `article-${slug}-${locale}`,
+      query: { lang: locale },
+    })
+    langSwitch.value = { available: Boolean(data.value?.hasTranslation), fallback: '/en/blog' }
+    return
+  }
+
+  if (categoryMatch) {
+    // A category's own translation only gates that specific label — the
+    // switch always lands somewhere useful (a filtered, possibly empty,
+    // article list), so it's always shown.
+    void useFetch<Category>(`/content/categories/${categoryMatch[1]}`, {
+      key: `category-${categoryMatch[1]}-${locale}`,
+      query: { lang: locale },
+    })
+    langSwitch.value = { available: true, fallback: '/en/blog' }
+    return
+  }
+
+  if (bare === '/come-difendersi-dal-corralito') {
+    langSwitch.value = { available: false, fallback: '/en' }
+    return
+  }
+
+  langSwitch.value = { available: true, fallback: '/en' }
+})