[UX] - Fix: Browser back in assistant builder

[JulesBelveze]

Browser back should ideally bring user back the previous state (from "select data source" to "assistant builder", from "select a Notion data source" to "select data source" and so on)

[Duncid]

@PopDaph I think you tackled this one did you not?

[PopDaph]

iirc I fixed part of it, there was still a bug left on the datasource modal but that is supposed to disappear with vault since we're reworking this modal so we agreed to keep living a bit with it