Add an option to move downloaded files/episodes

### What problem does this address?

I subscribed to some shows, that "depublish" their episodes after a number of new epsiodes or a certain amount of time. These episode show up as downloaded on my main device" but aren't playable on devices without Auto-Download (due to storage usage) or on the web player.

In case of loss or defect of my main device, I can't listen to these episodes any more.

### What is your proposed solution?

I suggest to provide a function to move downloaded files to a given point on the device (to manually transfer them) or for Pro Users to upload to personal File Storage to sync that files to any used device

### Did you search for existing feature suggestions?

- [X] I have searched for existing feature suggestions.

The issue names no files, tests, or entry points; begin by mapping Android's downloaded-episode storage and device-sync behavior. Clarify whether the goal is local transfer, personal File Storage upload, or both, then define storage, permissions, sync, and playback acceptance criteria before implementation.

Written by the indexing model from the issue text.