API: Compounded price formatting issue

Description

<img width="707" height="334" alt="Image" src="https://github.com/user-attachments/assets/18ef032e-52de-496a-aa58-88096a8371e4" />

The price should be rounded off to 2 decimal places. The change should be made in the API.

To the compounded price, add (1 month) if it's a monthly billing. Add (12 months) if its annual

<!-- upstream-issue: keyshade-xyz/keyshade#1130 -->