fix(webhooks): build events initiator_merchant_id indexes concurrently and allow platform JWT on profile update
- Drop the non-concurrent CREATE INDEX statements from
migrations/2026-04-09-103802_add_initiator_merchant_id_to_events
(introduced in #11643) so deployments no longer take an ACCESS
EXCLUSIVE lock on the events table when adding these indexes.
- Add a new migration that recreates both indexes with
CREATE INDEX CONCURRENTLY and runs outside of a transaction.
- Enable allow_platform on the v1 profile_update JWT auth so platform
profiles can update their own webhook endpoint configuration.
Fixes bugs introduced in #11643.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>