feat: send language in payment requests for localized descriptions

- Add language field to balance topup and landing purchase requests
- Cap news article featured image height with max-h-96

Cherry-picked from PR #362 (without favicon change — files don't exist)

src/pages/NewsArticle.tsx

@@ -408,7 +408,7 @@ export default function NewsArticlePage() {
           <img
             src={article.featured_image_url}
             alt={article.title}
-            className="h-auto w-full rounded-xl object-cover"
+            className="max-h-96 w-full rounded-xl object-cover"
             loading="eager"
             fetchPriority="high"
           />

src/pages/QuickPurchase.tsx

@@ -927,6 +927,7 @@ export default function QuickPurchase() {
       contact_type: detectContactType(contactValue),
       contact_value: contactValue.trim(),
       payment_method: paymentMethod,
+      language: i18n.language,
       is_gift: isGift,
     };