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.

pocketbase/pb_migrations/1757500002_add_english_fields.js

@@ -0,0 +1,29 @@
+/// <reference path="../pb_data/types.d.ts" />
+
+// Adds optional English counterparts to the manually-authored Italian fields,
+// on the same record (same slug, same cover, same category, same
+// publishedAt) — see docs/content-model.md. An article/category with no
+// translation yet simply leaves these blank; nothing else changes.
+migrate((app) => {
+  const articles = app.findCollectionByNameOrId('articles')
+  articles.fields.add(
+    new TextField({ name: 'titleEn', max: 160 }),
+    new TextField({ name: 'contentEn', max: 10000 }),
+    new TextField({ name: 'coverAltEn', max: 200 })
+  )
+  app.save(articles)
+
+  const categories = app.findCollectionByNameOrId('categories')
+  categories.fields.add(new TextField({ name: 'nameEn', max: 160 }))
+  app.save(categories)
+}, (app) => {
+  const articles = app.findCollectionByNameOrId('articles')
+  articles.fields.removeByName('titleEn')
+  articles.fields.removeByName('contentEn')
+  articles.fields.removeByName('coverAltEn')
+  app.save(articles)
+
+  const categories = app.findCollectionByNameOrId('categories')
+  categories.fields.removeByName('nameEn')
+  app.save(categories)
+})