Can I bake a finished Ginger Bread House
This seems like a bit of a catch-22. 

If you bake the assembled gingerbread house for an extra 90 minutes at 90°C, the gingerbread cookies will possibly/likely become dried out, hard, and inedible. 

Candies and decoration may become similarly dried out and inedible. Some chocolate or gummy candies may melt, even at the relatively low oven temperature. 

I wouldn't consider baking the completed gingerbread house as a means to make it edible. I think it would have quite the opposite effect (though, I've never done it).

I think the real question is whether the raw egg whites used are safe to consume as is. As mentioned in one of the comments, this can vary depending on where/how the eggs are sourced and what country's regulations you're listening to. Here in the US, the FDA warns against eating raw eggs, but US eggs are quite different than European eggs due to the differences in cleaning/processing eggs between the farm and table.