CHW-1404 PlanChangeRateLimited

too many plan changes from this organization — please wait and try again

Default message: too many plan changes from this organization — please wait and try again
HTTP status: 429 (client)
Reason: RATE_LIMITED

Problem. /api/billing/checkout rejected rapid repeated calls from the same org. Cause. The planChangeLimiter caps how many checkout requests an org can make in a window to keep the Paddle dashboard clean and guard against checkout-link abuse. Fix. Respect the Retry-After header (also exposed as retry_after_seconds on the error fields) and try again after it elapses. HTTP 429.