Notes and description fields on groups, flows, stages, and policies

## What

notes/description fields: #6697 is groups-only; #8966 wants comments on flows/stages/policies too. Close the narrower extra as Duplicate of the broader keeper.

## Want

- Notes/description fields: #6697 is groups-only
- #8966 wants comments on flows/stages/policies too

## Ideas this came from

- [#6697 Allow Comments on Groups](https://github.com/goauthentik/authentik/issues/6697) — We have multiple groups which we use for role-based access. IT would be nice if the group overview could show some description of what a specific group does (es
- [#8966 Comments, Notes, or Description fields.](https://github.com/goauthentik/authentik/issues/8966) — I may be missing something obvious, but I have search the documentation and google. Is there a way to record a description or comments for custom flows or stage

Review issues #6697 and #8966 first. This issue explicitly identifies #8966 as the broader keeper and asks that the narrower request be treated as a duplicate, so no implementation files, tests, or completion criteria are provided here.

Written by the indexing model from the issue text.