fix: chat-file, dark mode, etc.

[thun888]

修复以下内容：

1. 手动切换深色模式时顶栏异常高亮显示 #593
2. 聊天对话框中文件file类修改为chat-file类，避免错误处理gist(embed时)
3. image标签不显示下载按钮 #607
4. loading的失败后变成3个占位框 #588
5. 结构化数据中sameAs来源修正为使用 structured_data.links
6. 结构化数据中添加自动补全logo链接，以避免搜索引擎无法处理相对路径

[bolt-new-by-stackblitz[bot]]

Run & review this pull request in StackBlitz Codeflow.

[request-info[bot]]

The maintainers of this repository would appreciate it if you could provide more information.