Investigate feasibility of supporting a configurable reward schedule for staking

Since long-term returns are dictated by the reward rate schedule the protocol implements, we should add the ability for Playgrounds users to simulate different reward rate schedules

The reward rate frameworks like OIP-18 and KIP-3 don't offer specific guidance about when exactly the reward rate will be reduced, so we need to offer a more "open-ended" solution that allows users to configure when they think the reward rate will be reduced and what level it will be reduced to

We could bake in a "default" schedule based on conservative estimates for each protocol, and then allow the user to tweak these based on what they think would happen (both adding more "steps" and adjusting the rate of each step)

This will be a complex implementation, treat this as a discovery ticket to assess the difficulty and map out if this makes sense

Examine the existing staking simulation code in the repository to understand the current reward rate logic. Look for configuration files or models where reward schedules are defined. The goal is to design a flexible system that allows users to define custom step‑down schedules, with a default based on conservative protocol estimates.

Written by the indexing model from the issue text.