Add setting to switch direction of autoplay

### Description

Hi, first of all, excellent app, I've switched to it recently and it's genuinely great!! One feature that sets it apart for me compared to for example AntennaPod is autoplay as I tend to binge podcasts.

The one thing I think it is missing and I would love to see is to be able to change the direction of autoplay. The way it works (as far as I understand) is that when the end of an episode is reached the "next" episode of that same podcast is played if there is one (skipping archived ones etc.) with "next" meaning the one underneath it in the list of episodes and it respects whatever sorting one selects (that is great). It would be great if there was (ideally a podcast specific) setting that would change "next" to be the episode above the current one.

This would be very useful for me as I often like to have newest episodes of a podcast on top, however when playing I would like the episodes to play chronologically and thus upwards instead of downwards. This seems like it should be a pretty simple feature (though I'm sure it's more complex in practice).

### Screenshots or screen recording

_No response_

### Did you search for existing list?

- [x] I have searched for existing issues.

Start by locating the autoplay logic that selects the next episode and the existing podcast-specific settings. Trace how episode sorting is respected, then determine where the direction setting belongs. Done means users can choose upward or downward autoplay and playback follows that choice for the podcast.

Written by the indexing model from the issue text.