Posts from JP connected sites without a JP paid plan are not indexed in tags feeds

Internal discussion ref: p1705052443959929-slack-C0180B5PRJ4

Expected behavior

When a user posts to a JP-connected site using a tag, the post should appear in that tag feed in the reader.

Actual behavior

When a user posts to a JP-connected site using a tag, the post appears in that tag feed in the reader only if there is an active JP paid plan on that site.

This is due to some filtering in place in the backend. Especially thinking of the prompts "View all answers" scenario, that shows posts for the daily prompt tag, we might consider showing a nudge "to educate the user that their blog can be included in more places with a plan".

(NOTE: if we go this way, for it to be reliable and future-proof, we should make it driven by a flag sent by the API)

Tested on [S23], Android [14], JPAndroid / WPAndroid [24.0]

Ref: iOS twin issue

Start at the Reader's tag-feed entry point and trace the backend filtering that excludes posts from JP-connected sites without a paid plan. Check the related iOS issue and the API behavior before deciding where the change belongs. Done means eligible posts appear in the tag feed regardless of the site's JP paid-plan status, with any prompt nudge driven by an API flag if that approach is retained.