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/search.go

@@ -0,0 +1,65 @@
+package xiaohongshu
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"net/url"
+	"time"
+
+	"github.com/go-rod/rod"
+)
+
+type SearchResult struct {
+	Search struct {
+		Feeds FeedsValue `json:"feeds"`
+	} `json:"search"`
+}
+
+type SearchAction struct {
+	page *rod.Page
+}
+
+func NewSearchAction(page *rod.Page) *SearchAction {
+	pp := page.Timeout(60 * time.Second)
+
+	return &SearchAction{page: pp}
+}
+
+func (s *SearchAction) Search(ctx context.Context, keyword string) ([]Feed, error) {
+	page := s.page.Context(ctx)
+
+	searchURL := makeSearchURL(keyword)
+	page.MustNavigate(searchURL)
+	page.MustWaitStable()
+
+	page.MustWait(`() => window.__INITIAL_STATE__ !== undefined`)
+
+	// 获取 window.__INITIAL_STATE__ 并转换为 JSON 字符串
+	result := page.MustEval(`() => {
+			if (window.__INITIAL_STATE__) {
+				return JSON.stringify(window.__INITIAL_STATE__);
+			}
+			return "";
+		}`).String()
+
+	if result == "" {
+		return nil, fmt.Errorf("__INITIAL_STATE__ not found")
+	}
+
+	var searchResult SearchResult
+	if err := json.Unmarshal([]byte(result), &searchResult); err != nil {
+		return nil, fmt.Errorf("failed to unmarshal __INITIAL_STATE__: %w", err)
+	}
+
+	return searchResult.Search.Feeds.Value, nil
+}
+
+func makeSearchURL(keyword string) string {
+
+	values := url.Values{}
+	values.Set("keyword", keyword)
+	values.Set("source", "web_explore_feed")
+
+	return fmt.Sprintf("https://www.xiaohongshu.com/search_result?%s", values.Encode())
+}