feat(findings): 发现页支持导出（Markdown 单文件/分文件zip、CSV、JSON，按筛选/全部/勾选）

- 后端新增 GET /exploration/findings/export：按 scope(filtered|all|selected) ×
  format(md-single|md-zip|csv|json) 导出，md-zip 用 archive/zip 后端打包
- db.ListFindingsForExport：带完整 report、不分页，按严重等级+时间排序
- report/findings.go：汇总/单条 Markdown、安全文件名、带 BOM 的 CSV 渲染
- 前端发现页加行勾选 + 导出弹窗（范围×格式）；复用 lib/utils.copyText
- 顺带修复报告复制在 HTTP 非安全上下文失效（execCommand 降级）+ 复用 CopyButton

Claude-Session: https://claude.ai/code/session_01Bs2rrsVHUBTxRusm9espwB

db/findings.go

@@ -210,6 +210,57 @@ func (d *DB) ListFindingsPage(f FindingFilter, page, pageSize int) ([]*DBFinding
 	return out, total, err
 }
 
+// ListFindingsForExport returns findings for the 发现 page 导出功能，携带完整
+// report 字段、不分页。ids 非空时按这批 finding id 精确导出(勾选导出),忽略
+// filter;ids 为空时按 filter 导出(导出当前筛选/全部)。结果按严重等级降序、
+// 再按时间倒序,与「导出汇总报告」的分组顺序一致。
+func (d *DB) ListFindingsForExport(f FindingFilter, ids []int64) ([]*DBFinding, error) {
+	const order = `ORDER BY CASE f.severity WHEN 'critical' THEN 4 WHEN 'high' THEN 3 WHEN 'medium' THEN 2 WHEN 'low' THEN 1 ELSE 0 END DESC, f.created_at DESC`
+	cols := findingSelectCols + `, COALESCE(f.report, '')`
+
+	var q string
+	var args []any
+	if len(ids) > 0 {
+		ph := make([]string, len(ids))
+		for i, id := range ids {
+			ph[i] = fmt.Sprintf("$%d", i+1)
+			args = append(args, id)
+		}
+		q = `SELECT ` + cols + `
+			FROM findings f
+			LEFT JOIN tasks t ON f.task_id = t.id
+			WHERE f.id IN (` + strings.Join(ph, ",") + `)
+			` + order
+	} else {
+		where, wargs := f.where()
+		q = `SELECT ` + cols + `
+			FROM findings f
+			LEFT JOIN tasks t ON f.task_id = t.id` + where + `
+			` + order
+		args = wargs
+	}
+
+	rows, err := d.Query(q, args...)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+
+	var out []*DBFinding
+	for rows.Next() {
+		f := &DBFinding{}
+		var aidsJSON string
+		if err := rows.Scan(&f.ID, &f.TaskID, &f.NodeID, &f.VulnClass, &f.Name, &f.Severity,
+			&f.Summary, &f.Evidence, &f.Worker, &aidsJSON, &f.Status, &f.CreatedAt,
+			&f.TaskDescription, &f.Report); err != nil {
+			return nil, err
+		}
+		_ = json.Unmarshal([]byte(aidsJSON), &f.AssetIDs)
+		out = append(out, f)
+	}
+	return out, rows.Err()
+}
+
 // FindingStats is the whole-table aggregate powering the 发现 page's stat cards
 // and vuln-class filter — computed server-side so it stays exact regardless of
 // pagination.