Duplicate sending

Hi ! I found a little bug when using the app.
Btw, copyparty is really cool, thanks for that !

### Describe the bug
Once a file has finished uploading, if the screen is rotated, the upload will start again.

### To Reproduce
Upload one or more files. Once the 'Finished' menu pops up, rotate the screen and the upload will start again.

### Expected behavior
Once the upload is finished, do not upload again when the screen rotates.

### Client details
if the issue is possibly on the client-side, then mention some of the following:
* the device type and model: Xiaomi Poco F4
* OS version: Android 14 UKQ1.231207.002
* party-up version: 1.7.0
* party-up on upload success: Show menu (default)

檢查 Android 應用程式中的上傳 Activity 或 Fragment 生命週期。螢幕旋轉時會發生此 bug，這會觸發組態變更並重新啟動 Activity。檢查上傳狀態如何在旋轉過程中持久化——很可能是在 onSaveInstanceState 和 onRestoreInstanceState 中。修正方式是：如果上傳已經完成，則阻止上傳重新啟動。執行應用程式、上傳檔案、旋轉螢幕，並觀察行為以確認此問題。

由索引模型根據 Issue 內容生成。