Fix: Queried category should appear first in post category list when filtering by category

[Copilot]

When a post belongs to multiple categories and a visitor filters posts by a specific category, the post card displays a random category name instead of the one being filtered — because the backend returns all post categories in stored order and templates display the first one.

Changes

• PostFinderImpl.listByCategory(): After fetching posts, reorder each post's categories list so the queried category appears first, followed by matched child categories, then remaining categories.
• PostFinderImpl.list(Map params): Same fix applied when categoryName filter is present.
• sortCategoriesByFilter() helper: Extracted shared sorting logic; uses HashSet for O(n log n) sort instead of O(n²·m).

// Before: post filtered by "cat1" could return categories as ["cat2", "cat1"]
// After: categories are ["cat1", "cat2"] — queried category is always first
private static void sortCategoriesByFilter(ListedPostVo postVo, String queriedCategoryName,
    List<String> matchedCategoryNames) {
    var matchedSet = new HashSet<>(matchedCategoryNames);
    reordered.sort((a, b) -> {
        boolean aExact = queriedCategoryName.equals(nameA);
        boolean bExact = queriedCategoryName.equals(nameB);
        // exact match first, then child matches, then rest
        ...
    });
}

• Tests: Added ListByCategoryTest covering multi-category reordering and single-category no-op cases.

What type of PR is this?

/kind bug
/kind regression

What this PR does / why we need it:

When filtering posts by category on the visitor-facing site, each post's categories list was returned in stored order. Since templates display the first category, a post with ["cat2", "cat1"] filtered by cat1 would show cat2 on the card. The fix reorders categories per-post so the filtered category is always first.

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

The reordering is applied only in the two category-filtered list paths (listByCategory and list(Map) with categoryName). Other listing paths (by tag, owner, archives) are unaffected.

Does this PR introduce a user-facing change?

Fix post card displaying wrong category name when filtering posts by a category that the post shares with other categories.

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Original prompt

---

This section details on the original issue you should resolve

<issue_title>当给文章选择多个分类时，文章发布后，文章的分类名称随机显示</issue_title>
<issue_description>### 前置条件

• 已经在 issues 列表中搜索了相关问题。
• 这是 Halo 项目本身存在的问题，如果是非项目本身的问题（如：安装部署问题），建议在 Discussions 提交。
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• 如果是插件和主题的问题，请在对应的插件和主题仓库提交。

系统信息

• 外部访问地址:
• 启动时间: 2025-06-11 17:04
• 版本: 2.20.21
• 构建时间: 2025-05-15 14:17
• Git Commit: 2ca731f
• Java: IBM Semeru Runtime Open Edition / 21.0.7+6-LTS
• 数据库: MySQL Community Server - GPL / 8.1.0
• 操作系统: Linux / 5.15.0-136-generic
• 已激活主题: Earth 1.12.4
• 已启动插件:
  • 瞬间 1.9.0
  • 封面图 1.0.1
  • Vditor 编辑器 1.9.1
  • RSS 1.3.0
  • Sitemap 1.1.2
  • 搜索组件 1.6.2
  • 评论组件 2.5.1
  • 应用市场 1.8.0

使用的哪种方式运行？

Docker

发生了什么？

当给文章选择多个分类时，文章发布后，文章的分类名称随机显示

复现步骤

1、新建文章，给它添加2个分类，文章分类1、文章分类2
2、文章发布，进入访客主页，查看刚才发布的文章
3、通过访客主页的文章分类菜单筛选不同的文章（卡片）
4、刚才那篇文章卡片顶端显示的分类名称随机显示，一会显示【文章分类1】、一会儿显示【文章分类2】。我在筛选文章分类1 的时候，它反而显示成文章分类2，筛选文章分类2的时候，反而显示成文章分类1。这个是随机的，有时候显示正常。

期望结果：
当文章同时属于2个分类时，在筛选文章列表时，文章卡片顶端显示的分类名称应该是当前分类，而不是随机显示。
注意：使用的主题是2.0默认的earth。

相关日志输出

附加信息

No response</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes 当给文章选择多个分类时，文章发布后，文章的分类名称随机显示 #7537

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[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
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0.0% Coverage on New Code
0.0% Duplication on New Code

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