App: Storage access framework

The new file saving framework has a disadvantage to me. I can’t overwrite existing routes any more by exporting the actual route. Even if the name is the same as an existing file, it doesn’t ask for overwriting, it just saves it as another file. I do like the previous way by asking to overwrite the existing file more

an additional disadvantage is that the new files are not connected to the kurviger app automatically any more