Notifications should be Space-separated in some way

Summary: I get Notifications for two different Spaces right now (SI FAQ and SI Playtesting). When I click the bell, it shows me all Notifications from both those Spaces, interwoven. This is both deucedly inconvenient and a UX problem that could lead to accidental identity bleed. Even worse, it clears the "unseen" flag on all the Notifications, which means if one Space has important stuff I need to pay attention to I effectively lose my Notifications from the other Space unless I click through to each and every one and bookmark it to go back to it later.

This needs a bit of technical investigation and design, but is an entirely valid point so we should get it done.