File upload & download via WebView for Android and iOS

### What is the problem or limitation you are having?

Hi, thank you for this great project! I am currently working on a project where I need to upload and download files via the WebView. I am use Flask as the backend and serve the web pages via the WebView.

### Describe the solution you'd like

The solution would be just like it functions in a normal web browser i.e. clicking on a download link should download the file in the Downloads folder. For uploading a file, it should open up the file picker and allow the user to choose a file.

### Describe alternatives you've considered

-

### Additional context

_No response_

Start by locating the Android and iOS WebView entry points and checking how the existing WebView serves pages from the Flask backend. Compare current behavior with the requested browser-like file picker, upload, and Downloads-folder flows; done means both platforms support those flows, with platform-specific behavior verified.

Written by the indexing model from the issue text.