The dress code at the four star Hotel Bruno is smart-casual, so wearing a smart T-shirt and jeans after skiing is fine. Some people like to dress up more for dinner. The hotels tend to be very warm in comparison with the outside temperature, so you are unlikely to need to wear warm jumpers in the hotel, a blouse or t-shirt will be warm enough when sitting in the lounge or restaurant, as will lightweight shoes. Warm jumpers and boots are only really needed when going walking outdoors.
As it is a four star hotel, you are expected to be dressed when coming to the restaurant for breakfast and dinner, so, for example, wearing your pyjamas, shorts, or flip-flops in the restaurant are not appropriate and you may be asked to change.