Write a function that optimizes a given process within a system.
Model the process as a directed weighted graph and return the minimum-cost path from start to target using at most max_steps transitions. The input is a dictionary mapping each node to [next_node, cost] pairs. Return {"cost": number, "path": [nodes]}, or None when the target cannot be reached within the step limit.
def optimize_process(transitions, start, target, max_steps):