新增“截图覆盖翻译”功能，类似微信截图翻译

[HaibinZhang1]

Please confirm the following:

• I have carefully read the README
• I have searched through the issues page and didn't find a similar feature request.(Including issue that has been closed)
• Easydict has been upgraded to the latest version
• I understand and agree to the above, and understand that the project maintainer has limited energy, issues that do not follow the rules may be ignored or closed directly

Feature description

我计划实现一个“截图覆盖翻译”功能

Use case

类似微信截图翻译：

• 长按快捷键拖动鼠标，框选屏幕区域
• OCR 获取文字和坐标
• 翻译后按原位置覆盖显示
• Esc 关闭，不保存截图

我会尽量保持独立入口，不影响现有截图翻译逻辑。完成后提交 PR。

Proposed solution (optional)

No response

Are you willing to submit a PR to implement this feature

• I'm willing to submit PR to implement this feature

[Issues-translate-bot]

Bot detected this issue is not in English and translated it automatically.

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Title: Added "screenshot overlay translation" function, similar to WeChat screenshot translation

[github-actions]

Hello HaibinZhang1, Thank you for your first issue contribution 🎉