sameervaghela2121/monthstick-senior-mern-assessment ? reverse-engineered prompt

Build me a fix pass for this existing MonthStick renewal dashboard and API.

It’s a subscriptions renewal app, and I need the known production issues cleaned up without changing the overall product. Please make renewal runs safe so the same subscription and month can never create duplicate renewal events, even if two requests happen at once. The history screen should always show the right month, load cleanly, and not flash old data when I switch months quickly. Also add a Status filter for renewal history so I can view All, Scheduled, Charged, or Failed events, and make sure paging still works correctly with that filter.

Please validate bad input properly too, like month, page, page size, status, and event updates, and return clear 400 errors instead of crashing. If you can, improve the history endpoint so it stops doing repeated database work and feels faster. There are also a few reported finance and payments issues around totals, time zones, retries, and webhook handling, so investigate those and fix what you can. Look up current docs online if you need to.