feat: 添加搜索功能 (#16)

- 新增 SearchFeeds 服务方法，支持关键词搜索小红书内容
- 添加 search_feeds MCP 工具，提供搜索接口
- 新增 /api/v1/feeds/search API 端点
- 实现搜索页面的浏览器自动化操作
- 优化 MCP 协议支持，处理 notifications/initialized 和 notifications/cancelled 通知
- 更新文档，添加搜索功能说明和使用示例
- 重构类型定义，优化数据结构

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-authored-by: Claude <noreply@anthropic.com>

xiaohongshu/feeds_test.go

@@ -35,7 +35,6 @@ func TestGetFeedsList(t *testing.T) {
 		require.NotEmpty(t, feed.ID, "Feed ID should not be empty")
 		require.NotEmpty(t, feed.ModelType, "ModelType should not be empty")
 		require.NotEmpty(t, feed.XsecToken, "XsecToken should not be empty")
-		require.NotEmpty(t, feed.TrackID, "TrackID should not be empty")
 		require.NotEmpty(t, feed.NoteCard.Type, "NoteCard Type should not be empty")
 		require.NotEmpty(t, feed.NoteCard.DisplayTitle, "DisplayTitle should not be empty")
 		require.NotEmpty(t, feed.NoteCard.User.UserID, "User ID should not be empty")