fix: 搜索走 SearXNG + 工具调用分页修复

- ai-core DevTools 启动配置补充 SEARXNG_URL，避免回退到 DuckDuckGo 导致超时
- 工具调用 API 加入 offset 分页，修复 page 参数不生效问题
- 响应新增 total_pages 字段，修复前端分页栏不渲染

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

backend/pkg/plugins/manager/registry.go

@@ -230,25 +230,35 @@ func (r *ToolRegistry) UnregisterAll(toolIDs []string) {
 	}
 }
 
-// GetCallLogs 获取工具调用记录（最新在前，支持按工具名过滤）
-func (r *ToolRegistry) GetCallLogs(toolName string, limit int) []CallLogRecord {
+// GetCallLogs 获取工具调用记录（最新在前，支持按工具名过滤、分页）
+func (r *ToolRegistry) GetCallLogs(toolName string, limit, offset int) ([]CallLogRecord, int) {
 	all := r.callLog.getAll()
+
+	// 过滤
+	var filtered []CallLogRecord
 	if toolName == "" {
-		if limit > 0 && limit < len(all) {
-			return all[:limit]
-		}
-		return all
-	}
-	filtered := make([]CallLogRecord, 0)
-	for _, rec := range all {
-		if rec.ToolName == toolName {
-			filtered = append(filtered, rec)
-			if limit > 0 && len(filtered) >= limit {
-				break
+		filtered = all
+	} else {
+		filtered = make([]CallLogRecord, 0)
+		for _, rec := range all {
+			if rec.ToolName == toolName {
+				filtered = append(filtered, rec)
 			}
 		}
 	}
-	return filtered
+
+	total := len(filtered)
+
+	// 分页
+	if offset >= len(filtered) {
+		return []CallLogRecord{}, total
+	}
+	page := filtered[offset:]
+	if limit > 0 && limit < len(page) {
+		page = page[:limit]
+	}
+
+	return page, total
 }
 
 // GetCallStats 获取工具调用统计