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/pages/category/[slug].vue

@@ -1,71 +1,3 @@
-<script setup lang="ts">
-import type { ArticleSummary, Paginated, Category } from '#shared/types/blog'
-
-const route = useRoute()
-const slug = route.params.slug as string
-
-const page = computed(() => {
-  const value = Number(route.query.page)
-  return Number.isInteger(value) && value > 0 ? value : 1
-})
-
-const { data: category } = await useFetch<Category>(`/content/categories/${slug}`)
-
-if (!category.value) {
-  throw createError({ statusCode: 404, statusMessage: 'Category not found', fatal: true })
-}
-
-const { data, error } = await useFetch<Paginated<ArticleSummary>>('/content/articles', {
-  query: { page, category: slug },
-})
-
-const { public: config } = useRuntimeConfig()
-const canonical = computed(
-  () => `${config.siteUrl}${route.path}${page.value > 1 ? `?page=${page.value}` : ''}`
-)
-
-useSeoMeta({
-  title: category.value.name,
-  description: () => `Tutti gli articoli nella categoria ${category.value?.name ?? ''}.`,
-  ogType: 'website',
-})
-
-useHead({ link: [{ rel: 'canonical', href: canonical }] })
-</script>
-
 <template>
-  <div>
-    <header class="page-header">
-      <p class="kicker">Categoria</p>
-      <h1>{{ category?.name }}</h1>
-    </header>
-
-    <p v-if="error">Non è stato possibile caricare gli articoli. Riprova più tardi.</p>
-
-    <p v-else-if="!data?.items.length">Non ci sono articoli in questa categoria.</p>
-
-    <template v-else>
-      <ul class="card-grid">
-        <li v-for="article in data.items" :key="article.slug">
-          <ArticleCard :article="article" />
-        </li>
-      </ul>
-
-      <nav v-if="data.pageCount > 1" class="pagination" aria-label="Paginazione">
-        <NuxtLink v-if="data.page > 1" :to="{ query: { page: data.page - 1 } }" rel="prev">
-          Pagina precedente
-        </NuxtLink>
-        <span class="muted">
-          Pagina {{ data.page }} di {{ data.pageCount }}
-        </span>
-        <NuxtLink
-          v-if="data.page < data.pageCount"
-          :to="{ query: { page: data.page + 1 } }"
-          rel="next"
-        >
-          Pagina successiva
-        </NuxtLink>
-      </nav>
-    </template>
-  </div>
+  <CategoryView locale="it" />
 </template>