style(组件): 优化搜索图片网格卡片样式

- 调整圆角为更精致的 rounded 样式
- 更新背景色支持亮色/暗色主题
- 使用 ring 替代 border 实现更细腻的边框效果
- 添加精细的阴影层次感
- 优化 hover 状态的阴影过渡效果

src/components/features/SearchImagesGrid.tsx

@@ -136,11 +136,12 @@ export function SearchImagesGrid({
                 key={`${image.imageUrl}-${originalIndex}`}
                 className={cn(
                   'break-inside-avoid mb-3 group relative',
-                  'rounded-lg overflow-hidden',
-                  'bg-muted/30 dark:bg-muted/20',
-                  'border border-border/50',
+                  'rounded overflow-hidden',
+                  'bg-white dark:bg-zinc-900',
+                  'ring-1 ring-black/5 dark:ring-white/10',
+                  'shadow-[0_2px_8px_rgba(0,0,0,0.06)]',
                   'transition-all duration-200',
-                  'hover:shadow-lg hover:border-primary/30',
+                  'hover:shadow-[0_6px_20px_rgba(0,0,0,0.1)]',
                   !isLoaded && 'animate-pulse'
                 )}
               >