Backfill Subscription Periods

Backfill current_period_start/end for active subscriptions from Stripe. Iterates all active subscriptions with a stripe_subscription_id, fetches the subscription from Stripe, and syncs the billing period to the DB. Safe to re-run (idempotent).

curl -X POST "https://loading/api/sync/backfill-subscription-periods"

{
  "errors": 0,
  "skipped": 0,
  "status": "completed",
  "updated": 0
}