fix: 暗黑模式下封面图占位背景色跟随卡片颜色

components/LiveCard.tsx

@@ -43,7 +43,7 @@ export const LiveCard = React.memo(function LiveCard({
           source={{ uri: proxyImageUrl(item.cover) }}
           style={[
             styles.thumb,
-            { width: cardWidth, height: cardWidth * 0.5625 },
+            { width: cardWidth, height: cardWidth * 0.5625, backgroundColor: theme.card },
           ]}
           resizeMode="cover"
         />

components/VideoCard.tsx

@@ -34,7 +34,7 @@ export const VideoCard = React.memo(function VideoCard({ item, onPress }: Props)
       <View style={styles.thumbContainer}>
         <Image
           source={{ uri: coverImageUrl(item.pic, trafficSaving ? 'normal' : 'hd') }}
-          style={styles.thumb}
+          style={[styles.thumb, { backgroundColor: theme.card }]}
           resizeMode="cover"
         />
         <View style={styles.meta}>