feat: add timestamps to markdown export

[nDhnzr6r]

What this PR does

Before this PR:
Exported Markdown conversations do not include timestamps for each message.

After this PR:
Each message in the exported Markdown now includes its timestamp, making it easier to understand the conversation timeline.

Fixes #13272

Why we need it and why it was done in this way

The following tradeoffs were made:

The following alternatives were considered:

Links to places where the discussion took place:

Breaking changes

If this PR introduces breaking changes, please describe the changes and the impact on users.

Special notes for your reviewer

Checklist

This checklist is not enforcing, but it's a reminder of items that could be relevant to every PR.
Approvers are expected to review this list.

• PR: The PR description is expressive enough and will help future contributors
• Code: Write code that humans can understand and Keep it simple
• Refactor: You have left the code cleaner than you found it (Boy Scout Rule)
• Upgrade: Impact of this change on upgrade flows was considered and addressed if required
• Documentation: A user-guide update was considered and is present (link) or not required. Check this only when the PR introduces or changes a user-facing feature or behavior.
• Self-review: I have reviewed my own code (e.g., via /gh-pr-review, gh pr diff, or GitHub UI) before requesting review from others

Release note

[GeorgeDong32]

代码审查：需要修改 ❌

摘要

此 PR 包含大量语法错误，无法通过 pnpm lint 检查。这些错误是误将中文标点符号（逗号、句号）混入代码导致的。

已验证的问题

运行 pnpm lint 直接报错：

x Invalid Character `，`
  ,-[src/renderer/src/utils/export.ts:63:13]

x Invalid Character `，`
  ,-[src/renderer/src/store/settings.ts:425:29]

问题分类

类型	数量	示例
中文句号 。 代替 .	10+ 处	state。webdavSyncInterval
中文逗号 ， 代替 ,	15+ 处	localBackupAutoSync: false，
中文方法名	1 处	content.替换(...)

修复建议

1. 使用编辑器的搜索功能，查找所有 。 和 ，
2. 替换为英文 . 和 ,
3. 特别注意 content.替换 应改为 content.replace
4. 提交前务必运行 pnpm lint 验证

正面评价

✅ 新功能本身的实现逻辑是正确的：

• Redux 状态管理正确
• UI 设置和国际化完整
• 时间戳格式化逻辑合理

请修复语法错误后重新提交，感谢贡献！

[GeorgeDong32]

本地验证结果

✅ Build 检查：通过

• TypeScript 类型检查通过
• electron-vite 构建成功

❌ Lint 检查：失败

Error: 主模板文件 zh-cn.json 的键值未按字典序排序。

问题原因：新增的 show_timestamp 键位置不正确，未按字母顺序排列。

---

💡 修复建议

在提交前请执行以下命令：

# 修复 i18n 键值排序
pnpm i18n:sync

# 然后重新运行 lint 验证
pnpm lint

---

总结

检查项	状态
TypeScript 类型	✅ 通过
Build	✅ 通过
i18n 排序	❌ 需要修复

功能实现本身没有问题，只需要运行 pnpm i18n:sync 修复键值排序即可通过 lint 检查。

[nDhnzr6r]

Note

This issue/comment/review was translated by Claude.

What went wrong again???

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Original Content

？？？？？？？？？？？？？？？？
咋又错了

[nDhnzr6r]

Note

This issue/comment/review was translated by Claude.

How should this be modified?

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Original Content

这怎么改！。

[nDhnzr6r]

Note

This issue/comment/review was translated by Claude.

I need help!.

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Original Content

我需要帮助！。

[EurFelux]

原则上，在v2版本完成以前，我们不再接受需要添加新的持久化数据的PR。敬请理解