Refactor notifications as pop-ups

[in-op]

Currently notifications for successful CRUD operations - for example creating or deleting project notes, project fact types, and others - appear as a green section near the top of the page that shunts the rest of the content down. This is a bit jarring and could be missed if the page is long and the user is scrolled to the bottom. Instead, success and other similar notifications should be refactored as temporary pop-ups/toasts. These would be absolutely positioned on the page (probably at the top or bottom), and preferably with a nice simple animation when appearing and disappearing.