feat: fix hotspot test

services/lms-service/migrations/20260122000000_fix_user_grades_updated_at.sql

@@ -0,0 +1,4 @@
+-- Migration: Add updated_at to user_grades
+-- Required by fn_upsert_user_grade matching CMS-style upserts
+
+ALTER TABLE user_grades ADD COLUMN IF NOT EXISTS updated_at TIMESTAMPTZ NOT NULL DEFAULT NOW();