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/components/ArticleCard.vue

@@ -1,10 +1,15 @@
 <script setup lang="ts">
 import type { ArticleSummary } from '#shared/types/blog'
+import type { Locale } from '#shared/utils/locale'
+import { localePath } from '#shared/utils/locale'
 
-const props = defineProps<{ article: ArticleSummary }>()
+const props = withDefaults(defineProps<{ article: ArticleSummary; locale?: Locale }>(), {
+  locale: 'it',
+})
 
 const mediaUrl = useMediaUrl()
 const cover = computed(() => mediaUrl(props.article.cover))
+const href = computed(() => localePath(props.locale, `/blog/${props.article.slug}`))
 </script>
 
 <template>
@@ -14,7 +19,7 @@ const cover = computed(() => mediaUrl(props.article.cover))
     <NuxtLink
       v-if="cover"
       class="cover-link"
-      :to="`/blog/${article.slug}`"
+      :to="href"
       tabindex="-1"
       aria-hidden="true"
     >
@@ -29,12 +34,12 @@ const cover = computed(() => mediaUrl(props.article.cover))
     <p v-if="article.category" class="kicker">{{ article.category.name }}</p>
 
     <h2>
-      <NuxtLink :to="`/blog/${article.slug}`">{{ article.title }}</NuxtLink>
+      <NuxtLink :to="href">{{ article.title }}</NuxtLink>
     </h2>
 
     <p class="kicker date">
       <time :datetime="isoDate(article.publishedAt)">
-        {{ formatDate(article.publishedAt) }}
+        {{ formatDate(article.publishedAt, locale) }}
       </time>
     </p>
   </article>