Raspberry and Blackberry bushes. The entire plant is edible for rabbits and have some medicinal properties too. Blackberry will help with diarrhea and raspberry will help does during labor and improve lactation.
Blueberries are also good but might not play well in a food forest set up with their PH requirements. Strawberries too and if you aren't after a lot of fruit production you could do alpine type strawberries in shade under other berry bushes or trees.
Clover would be good for ground cover and its nitrogen fixing.
Pear trees come in dwarf varieties and the twigs and leaves can be fed like apple.
Rose leaves, flowers and hips are all a hit with my buns.
Cold hardy kiwi and grape vines and leaves are bunny safe.
Definitely through some herbs in there. My oregano, sage, mint, and catnip come back with a vengeance every year.
Also encourage some of the local rabbit safe weeds in your food forest. Plantain, dandelion, wild violets, purslane, etc.