ui(import-hub): 优化 skills.sh 卡片布局

- skills.sh 卡片改为列布局：
  顶部：图标+名称+URL（左侧）+ 访问按钮（右上）
  中部：URL 输入框（全宽）
  底部：检测名称预览 + 导入按钮（右下）
- 加大"说明"与平台卡片的间距（margin-top: space-xl）
- 导入按钮与名称预览在右侧同一行，间距更协调

frontend/src/pages/front/MarketPage.tsx

@@ -1067,16 +1067,16 @@ const mcpClient = new MCPClient({
           <div className="hub-platforms">
             {platforms.map(p => (
               <div key={p.id} className="hub-platform-card">
-                <div className="hub-platform-info">
-                  <div className="hub-platform-icon">
-                    <ImportIcon />
+                <div className="hub-platform-header">
+                  <div className="hub-platform-info">
+                    <div className="hub-platform-icon">
+                      <ImportIcon />
+                    </div>
+                    <div>
+                      <strong>{p.name}</strong>
+                      <span className="hub-platform-url">{p.url}</span>
+                    </div>
                   </div>
-                  <div>
-                    <strong>{p.name}</strong>
-                    <span className="hub-platform-url">{p.url}</span>
-                  </div>
-                </div>
-                <div className="hub-platform-actions">
                   <button
                     className="hub-visit-btn"
                     onClick={() => handleVisit(p.url)}
@@ -1086,38 +1086,42 @@ const mcpClient = new MCPClient({
                     </svg>
                     访问
                   </button>
-                  {appType === 'skill' ? (
+                </div>
+                {appType === 'skill' ? (
+                  <>
                     <div className="hub-import-col">
-                      <div className="hub-import-row">
-                        <input
-                          type="url"
-                          className="hub-url-input"
-                          placeholder="粘贴目标链接..."
-                          value={importUrl[p.id] || ''}
-                          onChange={e => setImportUrl(prev => ({ ...prev, [p.id]: e.target.value }))}
-                          disabled={importingId === p.id}
-                        />
+                      <input
+                        type="url"
+                        className="hub-url-input full"
+                        placeholder="粘贴目标链接..."
+                        value={importUrl[p.id] || ''}
+                        onChange={e => setImportUrl(prev => ({ ...prev, [p.id]: e.target.value }))}
+                        disabled={importingId === p.id}
+                      />
+                      <div className="hub-import-actions">
+                        {importUrl[p.id]?.trim() && (
+                          <span className="hub-name-preview">
+                            检测名称: <strong>{extractSkillName(importUrl[p.id], p.name)}</strong>
+                          </span>
+                        )}
                         <button
                           className="hub-import-btn"
                           onClick={() => handleImport(p.id)}
                           disabled={!importUrl[p.id]?.trim() || importingId !== null}
                         >
                           {importingId === p.id ? (
-                          <span className="hub-importing-text">
-                            <div className="audit-spinner tiny" />
-                            {statusMsg}
-                          </span>
-                        ) : '导入'}
-                      </button>
-                    </div>
-                    {importUrl[p.id]?.trim() && (
-                      <div className="hub-name-preview">
-                        检测名称: <strong>{extractSkillName(importUrl[p.id], p.name)}</strong>
+                            <span className="hub-importing-text">
+                              <div className="audit-spinner tiny" />
+                              {statusMsg}
+                            </span>
+                          ) : '导入'}
+                        </button>
                       </div>
-                    )}
-                  </div>
-                  ) : (
-                    <div className="hub-import-row">
+                    </div>
+                  </>
+                ) : (
+                  <div className="hub-import-col">
+                    <div className="hub-import-actions">
                       <button
                         className="hub-import-btn"
                         onClick={() => handleImport(p.id)}
@@ -1131,8 +1135,8 @@ const mcpClient = new MCPClient({
                         ) : '导入'}
                       </button>
                     </div>
-                  )}
-                </div>
+                  </div>
+                )}
               </div>
             ))}
           </div>