Show Best and Mean columns for 3x3x3 Blindfolded results

## Problem

On the competition results page for a 3x3x3 Blindfolded round, both summary columns are labeled `Best` and both render the single result. This is visible on Rubik's WCA European Championship 2026, 3x3x3 Blindfolded Round 1.

The round uses a best-of-3 format, so the current format-only column selection treats both summary columns as `single` even though WCIF/WCA Live also provides the mean in `average`.

## Expected behavior

The summary columns should be shown in this order:

1. `Best`, using `result.best` and the single record tag
2. `Mean`, using `result.average` and the average record tag

## Acceptance criteria

- 3x3x3 Blindfolded result tables render `Best` and `Mean`, not two `Best` columns.
- The two columns display the corresponding best and mean values.
- Record badges remain attached to the correct result type.
- Other event and round-format column behavior remains unchanged.
- Add regression coverage for a 3x3x3 Blindfolded best-of-3 round.

从 3x3x3 Blindfolded 的比赛结果页面的摘要列选择开始，跟踪 Best-of-3 格式如何将列映射到结果字段和记录标签。为此轮格式添加回归测试覆盖，然后验证表格显示来自 result.best 的 Best 和来自 result.average 的 Mean，同时其他事件和轮格式的行为保持不变。

由索引模型根据 Issue 内容生成。