style: fix mobile back button contrast and remove article image gradient

web/src/components/ArticleCard.tsx

@@ -36,8 +36,7 @@ export function ArticleCard({ article, onClick, onToggleRead, onToggleFavorite }
 
             {/* Image Placeholder with Gradient Overlay */}
             <div className="aspect-[16/10] overflow-hidden rounded-t-xl rounded-b-none bg-carbon-light relative mb-6">
-                {/* Gradient lowered to 30% height and reduced opacity to avoid covering too much image */}
-                <div className="absolute bottom-0 left-0 right-0 h-1/3 bg-gradient-to-t from-white via-white/60 to-transparent opacity-90 z-10"></div>
+
 
                 {/* Visual placeholder or real image */}
                 <div

web/src/components/MobileReaderView.tsx

@@ -113,7 +113,7 @@ export function MobileReaderView({ article, onClose, onToggleFavorite, onNext, o
                         e.stopPropagation();
                         onClose();
                     }}
-                    className="w-12 h-12 bg-carbon/80 backdrop-blur border border-white/10 text-white rounded-full shadow-lg flex items-center justify-center active:scale-90 transition-transform pointer-events-auto"
+                    className="w-12 h-12 bg-paper-white text-carbon-light shadow-2xl border border-white/10 rounded-full flex items-center justify-center active:scale-95 transition-all duration-300 pointer-events-auto hover:bg-nature"
                 >
                     <svg className="w-5 h-5" fill="none" viewBox="0 0 24 24" stroke="currentColor">
                         <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M6 18L18 6M6 6l12 12" />