Question: During wintertime it is often cold enough in my apartment that proofing takes much longer than in summer. I'd like to use my oven to create a warmer environment, in which the dough would rise faster. I can go 30-50 degrees celsius, the question is what temperature is safe and at what temperature will I actually start baking the dough. Is 50 degrees celsius still ok or not?

Answer: 
Rise from chilled @ 32C and keep rising until around 80-85% of desired height has been achieved. 
Return back to the chiller, it will continue to rise for a short time, keep in the chiller until dough is firm again and stable enough to take the weight of toppings.
I use the pull-out warming tray on my oven set on its lowest temperature. I've never actually checked the temperature, but its rather cool. I can easily touch the bottom of the drawer without any discomfort.