docs: update star history card

[xxynet]

Modifications / 改动点

The previous Star History card no longer renders because GitHub restricted access to star data, as shown in the reported screenshot. Replace it with the RepoStars embed, which renders without repository maintainers configuring a GitHub token.

• Updated the Star History embed in all seven localized README files.
• This is NOT a breaking change. / 这不是一个破坏性变更。

Screenshots or Test Results / 运行截图或测试结果

• Confirmed the reported Star History failure: GitHub restricted access to star data.
• Verified that all localized README files now use the RepoStars embed for AstrBotDevs/AstrBot.
• Ran git diff --check successfully.

---

Checklist / 检查清单

• 😊 This PR does not add a new feature and does not require prior feature discussion.
  / 此 PR 未新增功能，无需事先讨论。

• 👀 My changes have been well-tested, and "Verification Steps" and "Screenshots" have been provided above.
  / 我的更改经过了良好的测试，并已在上方提供了“验证步骤”和“运行截图”。

• 🤓 I have ensured that no new dependencies are introduced.
  / 我确保没有引入新依赖库。

• 😮 My changes do not introduce malicious code.
  / 我的更改没有引入恶意代码。

Summary by Sourcery

Restore repository star history displays across all localized README files.

Bug Fixes:

• Replace the broken Star History embeds with working RepoStars embeds across all localized README files.

Documentation:

• Update star history charts in the seven localized README files to use RepoStars.

[sourcery-ai]

Hey - I've found 1 issue

Prompt for AI Agents

Please address the comments from this code review:

## Individual Comments

### Comment 1
<location path="README.md" line_range="231" />
<code_context>
 <div align="center">

-[![Star History Chart](https://api.star-history.com/svg?repos=astrbotdevs/astrbot&type=Date)](https://star-history.com/#astrbotdevs/astrbot&Date)
+[![RepoStars](https://repostars.dev/api/embed?repo=AstrBotDevs%2FAstrBot&theme=dark)](https://repostars.dev/?repos=AstrBotDevs%2FAstrBot&theme=dark)

 </div>
</code_context>
<issue_to_address>
**nitpick:** The image alt text is reduced to the product name `RepoStars`, so when the chart cannot be loaded or is accessed by a screen reader, users are not told that the image is a repository star-history chart. The Spanish README also loses its previously descriptive localized alt text.

**Triggers:** When the image is unavailable or the README is consumed with a screen reader.

**Suggested fix:** Use a descriptive, localized alt text such as `Repository star history chart` rather than only `RepoStars`.

```suggestion
[![Repository star history chart](https://repostars.dev/api/embed?repo=AstrBotDevs%2FAstrBot&theme=dark)](https://repostars.dev/?repos=AstrBotDevs%2FAstrBot&theme=dark)
```
</issue_to_address>

Sourcery assessment

Approved.

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