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

檢查儲存庫中現有的質押模擬程式碼，以了解當前的獎勵率邏輯。尋找定義獎勵排程的設定檔或模型。目標是設計一個靈活的系統，允許使用者定義自訂的階梯式下調排程，預設值基於保守的協議估計。

由索引模型根據 Issue 內容生成。