Rate limit - Fire spark

Migration endpoints share one firewall rule: admin-migrate.

Limits

Limit	Value	Scope
Request rate	10 requests / 10 seconds	Both migrate endpoints, keyed by `x-merchant-id`
Concurrent processing	5 `PROCESSING` jobs	Per entity (`customers` vs `orders`)
Queue cap	100 `QUEUED` jobs	Per merchant + entity
Retention	30 days	Hard-delete `SUCCESS` / `FAILED` only

QUEUED and PROCESSING jobs are never deleted by retention.

Endpoints

POST /customers/migrate
POST /orders/migrate

429 responses

Code	When
`429`	More than 10 requests in 10 seconds for the merchant
`429` `queue_full`	The merchant already has 100 queued jobs for that entity

In production, a missing admin-migrate firewall rule fails closed with 503. Retry with backoff. Fix invalid rows from the job error list and POST the corrected batch again.