fix: 修复相似度检索卡片悬停效果层拦截点击事件的问题

- 在SimilaritySearchCard悬停效果层添加pointer-events-none，让点击事件穿透
- 修复外部链接按钮无法点击的问题
- 优化SimilaritySearchPanel布局为垂直排列

apps/desktop/src/components/similarity/SimilaritySearchCard.tsx

@@ -184,7 +184,7 @@ export const SimilaritySearchCard: React.FC<SimilaritySearchCardProps> = ({
         </div>
 
         {/* 悬停效果 */}
-        <div className="absolute inset-0 bg-gradient-to-br from-transparent via-transparent to-primary-50/20 opacity-0 group-hover:opacity-100 transition-opacity duration-500 rounded-lg"></div>
+        <div className="absolute inset-0 bg-gradient-to-br from-transparent via-transparent to-primary-50/20 opacity-0 group-hover:opacity-100 transition-opacity duration-500 rounded-lg pointer-events-none"></div>
       </div>
     </div>
   );

apps/desktop/src/components/similarity/SimilaritySearchPanel.tsx

@@ -91,7 +91,7 @@ export const SimilaritySearchPanel: React.FC<SimilaritySearchPanelProps> = ({
         </div>
 
         <div className="relative">
-          <div className="flex gap-3">
+          <div className="flex flex-col gap-3">
             <div className="flex-1 relative group">
               <input
                 ref={inputRef}