feat: add 30-day money back guarantee trust badge above complete order button

- Add green trust badge with checkmark icon above 'Complete Order' button
- Add translations for all locales (EN, SR, DE, FR)
- Badge includes: '30-Day Money-Back Guarantee' text
- Styled with green background and border to match trust/conversion theme

src/i18n/messages/fr.json

@@ -361,6 +361,7 @@
     "cashOnDeliveryDesc": "Payez lorsque votre commande est livrée à votre porte.",
     "processing": "En cours...",
     "completeOrder": "Finaliser la Commande - {total}",
+    "moneyBackGuarantee": "Garantie de remboursement de 30 jours",
     "orderSummary": "Résumé de la Commande",
     "qty": "Qté",
     "subtotal": "Sous-total",