feat: show full supported-platforms block on each downloader page

Replace the plain "looking for another platform?" text link at the
bottom of each per-platform page with the same SupportedPlatformsSection
used on the homepage, giving stronger internal linking between all
platform pages. Drop the now-unused otherPlatforms/browseAll strings.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

messages/it.json

@@ -96,9 +96,7 @@
     "heading": "Downloader {platform}",
     "subheading": "Incolla un link {platform} qui sotto e ottieni il tuo file in pochi secondi — gratis, senza account.",
     "aboutHeading": "Informazioni sullo scaricamento da {platform}",
-    "faqHeading": "FAQ downloader {platform}",
-    "otherPlatforms": "Cerchi un'altra piattaforma?",
-    "browseAll": "Sfoglia tutti i siti supportati"
+    "faqHeading": "FAQ downloader {platform}"
   },
   "downloaderPages": {
     "youtube": {