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/api/landings.ts

@@ -101,6 +101,7 @@ export interface PurchaseRequest {
   gift_recipient_type?: 'email' | 'telegram';
   gift_recipient_value?: string;
   gift_message?: string;
+  language?: string;
 }
 
 export interface PurchaseResponse {