Just remember, yeast evolved just like humans did and share the same temperature requirements. Roughly mid 50s to mid 90s. Anything above or below that and it gets uncomfortable...not deadly, just uncomfortable.
* The yeast packet will have a specification as to what is the optimum range. This is for the liquid environment they are in.
* Yeast produce heat, I have always measured a higher temp in the tank while active fermentation is going on than the ambient room or cooler. On a 3 or 5 gallon is probably 2F warmer.
* High temp stresses the yeast so you will see H2S production. So far when I have run hot the sulfur smell dissipates with time. High temp blows fruity aroma off, this is OK with reds since there normally are other flavors that aren’t heat sensitive. Above 110 I expect yeast to slowly die. Above 140 I expect yeast to be killed in 30 minutes.
* Low temp slows metabolism and they can become inactive. Some bacteria thrive at 40F so there is a risk of unintended infection. Low temp retains fruity aroma, therefore if you want high fruit cool well below ambient.
Your question was minimum, if I put in a lager yeast I could run 40F. A better question is what is practical? 40 could ferment dry in 8 weeks, 50 could be 2 weeks, 80 could be 2 days.
Safe- , wine is a preservative system, the combination of acid, alcohol and sulphites will prevent food poisoning organisms.
Drinkable- our goal is to produce a good tasting beverage, normally this happens. In the scheme of things alcohol is an intermediate in the life of a wine. Alcohol is trying to further break down primarily to vinegar and oxidized alcohol. We work to keep air off the wine which retains the pleasing flavors.