feat(ui): redesign landing page and update styling

Overhaul landing page design with updated CSS, Tailwind config, and
i18n translations across all supported languages.

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

assets/i18n/fr.json

@@ -224,7 +224,13 @@
     "documentation": "Documentation",
     "api_reference": "Reference API",
     "support": "Support",
-    "copyright": "2026 CERTifAI. Tous droits reserves."
+    "copyright": "2026 CERTifAI. Tous droits reserves.",
+    "pill_gdpr": "RGPD Natif",
+    "pill_self_hosted": "Auto-heberge",
+    "pill_eu": "Souverainete UE",
+    "preview_models": "Modeles Actifs",
+    "preview_tokens": "Tokens / Mois",
+    "preview_spend": "Depenses Totales"
   },
   "article": {
     "read_original": "Lire l'article original",