-- 0002_sessions_expires_index.sql — index sessions.expires_at.
--
-- The periodic sweep (and lazy cleanup) run `DELETE FROM sessions WHERE
-- expires_at <= ?`; without this index that is a full table scan. The table is
-- small at household scale, but the index is cheap insurance and keeps the sweep
-- O(expired) rather than O(all sessions).
CREATE INDEX idx_sessions_expires ON sessions (expires_at);