-- 0021 的回滚：先删索引、再删表（与 0019 的回滚同一顺序口径）。
-- 两张表都是本迁移新建的，回滚不触碰任何既有表。
DROP INDEX IF EXISTS idx_channel_event_counters_category;
DROP INDEX IF EXISTS idx_channel_event_counters_key;
DROP TABLE IF EXISTS channel_event_counters;
DROP INDEX IF EXISTS idx_channel_events_tier;
DROP INDEX IF EXISTS idx_channel_events_channel_id;
DROP INDEX IF EXISTS idx_channel_events_platform_category;
DROP INDEX IF EXISTS idx_channel_events_created_at;
DROP TABLE IF EXISTS channel_events;