Hailing a ride with your smartphone? That’s old news — ask any Uber, Lyft or Careem customer. But how about hailing a tractor? Just as urbanites may find it impractical to own a car but still need a ride once in a while, so, too, in the Indian countryside: To get the most from their land, small-scale farmers may need tractors and other machines from time to time, but they may not be able to…