Do include content type on status API model actually

This is mostly important when deleting and redrafting.

The comment on `apimodel.Status.Text` implies that it's not sent except in response to status deletion, but actually this doesn't seem to be the case; it also appears to be present in responses to creations and normal fetches and stuff. So I'm treating `ContentType` the same here.

internal/typeutils/internaltofrontend.go

@@ -1391,6 +1391,7 @@ func (c *Converter) baseStatusToFrontend(
 		Emojis:             apiEmojis,
 		Card:               nil, // TODO: implement cards
 		Text:               s.Text,
+		ContentType:        c.ContentTypeToAPIContentType(ctx, s.ContentType),
 		InteractionPolicy:  *apiInteractionPolicy,
 	}