I really like "Eat This Much". My partner and I have also been trying "Meal Prep Pro" which is a little prettier, a bit more expensive, and mobile only. The "Eat This Much" learning curve is a bit steeper, and it requires configuration, but it meets the "pantry leftovers" functionality you're looking for.
I have no association with "Eat This Much" other than being a customer and a fan.
I have no association with "Eat This Much" other than being a customer and a fan.