[Feature] Person sharing (v3.3.0-rc.2): standing share rules for "named people" / "everyone", with role and share-back

I have searched the existing feature requests, both open and closed, to make sure this is not a duplicate request. • Yes The feature Relates to: person sharing as shipped in v3.3.0-rc.2 (tested on a multi-user instance with a shared cluster group). The feature: turn person sharing from a one-time snapshot into a *standing share rule* (owner → recipient) that keeps applying as people are created or named. The problem Person sharing in 3.3.0 is a great step for households with several accounts on one library. In practice, though, sharing is a snapshot: "share all people" shares the people that exist today. Anyone created or named afterwards is not shared unless the owner repeats the share, which in practice means re-sharing after every scan or naming session. There is also no way to say "share the people I have actually named and ignore the unnamed clutter": today it is all people or hand-picked people. Proposal In the existing share dialog, o…