Rating podcasts + private subscription feeds

### Description

Currently you have to listen to podcast episodes before you can rate a podcast but there are a few podcasts that I subscribe to which have a personalized feed from a subscription service which I listen to instead. This is all fine, but because I listened to this one, I can't rate the public feed unless I listen to duplicate episodes first.

Is there any way to compare podcasts by URL, name, or similar podcast episodes to group all the ratings together so I can rate the actual podcast even though I've only listened to my personal subscription feed?

Case in point, I subscribe The Majority Report and the feed I listen to is from fans.fm, which has no ratings, but the main feed (https://play.pocketcasts.com/podcasts/629c4580-3082-012e-0bcc-00163e1b201c) has 3.4k ratings. In order to rate it, I would have to relisten to episodes I've already listened to even though they're essentially the same show.

Maybe the app could look at the title, description, or etc to see if they're similar and group them all together so the ratings on the private feed would count for the actual show?

Thanks! :)

### Screenshots or screen recording

_No response_

### Did you search for existing list?

- [x] I have searched for existing issues.

No files, tests, or entry points are named. Start by tracing how podcast identities, subscriptions, listening history, and ratings are represented and matched; done would require an agreed rule for relating private and public feeds without incorrectly merging unrelated podcasts, plus tests for that behavior.

Written by the indexing model from the issue text.