Smart Suggestions: Flag new suggestions & added topics

### Description

The broker view does still feel quite static, even though, under the covers it's doing a considerable amount of work

I don't think the value of the smart suggestions (schema agent) is effectively communicated via the UI. Instead, we should look to add a notification pill at the hierarchy view to show new suggestions are available, and _where_ they are available. Otherwise, the user has to manually explore every single topic before finding them.

Given the pace at which these can arrive, I'm not convinced websockets are going to be a good idea, so we may need to either poll infrequently, or await refresh as a first port of call.

### Which customers would this be available to

None

### Have you provided an initial effort estimate for this issue?

I have provided an initial effort estimate