Is it even possible to have habitable and volatiles? I thought those were only on gas planets and I've never seen a habitable one.
Yes, though it is uncommon or rare. In my current game, I have 125% Terran with low volatiles and moderate to high everything else (was 150% with decivilized, but Birdy's trick removed decivilized for 125%), and 75% Terran with some resources in the same system, somewhat close to core and west.
Closer to core and just south of Penelope's, 100% arid and 125% desert planets. None have all resources, but both together have them all.
Further southeast, I have 75% terran and 100% tundra with four out of five resources, missing rare ore.
Habitables can have trace or diffuse volatiles. With Industrial Planning, you only need Trace Volatiles to have enough for Fuel Production. Rare ore tops at moderate for habitables, unless it has high gravity, in which case it can go all the way up to ultrarich. You need at least moderate ore with Industrial Planning to satisfy demand for Refining.