Daily cron: process all due AppSumo subscription renewals.

Grants monthly credits on each user's signup anniversary date. Renewal dates are computed from users.created_at.

Stripe renewals are NOT processed here — they are handled exclusively by the invoice.payment_succeeded webhook to ensure credits are only granted after confirmed payment.

Robustness / ordering: every license is processed in its own savepoint and committed individually, so one bad record (or one bad pooled DB connection) is counted in appsumo_failed instead of failing the run. Deduplicates via the subscription_renewals table, so it is idempotent and may be re-run any time later the same day; its position in the LapisCRON schedule (e.g. right after the nightly backup dispatch) does not matter.

Called by LapisCRON or manually via dev_scripts.