feat(i18n): translate hardcoded article page strings to 5 locales

- Add ArticlePage namespace (backToNewsHub, backToNews, mediaGallery,
  joinLinkedIn, internalRelease) to all 5 locale message files
  (en, it, es, de, vec)
- Replace 5 hardcoded English strings in news/[slug]/page.tsx with
  getTranslations() calls

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

messages/en.json

@@ -184,6 +184,13 @@
     "page": "Page",
     "of": "of"
 },
+"ArticlePage": {
+    "backToNewsHub": "Back to News Hub",
+    "backToNews": "Back to News",
+    "mediaGallery": "Media Gallery",
+    "joinLinkedIn": "Join the conversation on LinkedIn",
+    "internalRelease": "Internal Corporate Release"
+},
 "AuthModal": {
     "b2bPortal": "B2B Portal",
     "signIn": "Sign In",