Replaces the in-memory sliding-window Map (reset on every restart, not
shareable across instances) with a login_attempts table (migration 016).
No Redis added - login is not a hot path, and this is a single indexed
range-scan query. Restart behavior confirmed for real:
platform/test/e2e-phase3a.js's rate-limiting test passes after a genuine
Platform API restart in the same run.
ced4568
addf474b70