Embed track number + casting support for the app

[madeofpendletonwool]

Discussed in https://github.com/madeofpendletonwool/PinePods/discussions/619

^{Originally posted by mhallor September 18, 2025} New user here, and already impressed with how pinepods embedds metadata in downloaded episodes, it already suits my needs much better than audiobookshelf or podfetch.

I use an external player (Emby) quite a lot, which relies fully on embedded metadata. The episodes currently get sorted by title rather than published date. This works alright for episodes that are numbered, but whenever there is a bonus episode or a feed drop or any other break from the regular numbering, those episodes end up out of order.

• If possible, I would appreciate if track number was an embedded field.
• it would also be helpful if this was an "absolute" track number (total number of tracks including non-numbered episodes)

Unrelated, support in the app for casting to devices including upnp/airplay would mean I could get rid of my external player altogether for podcast usage. I use speakers that don't support the casting options basically all podcast apps support (not sure what that actual protocol is. Chromecast, Miracast?), and only have support for upnp. Adding this to pinepods would set it apart from others.