Class overview

Student	Lessons	XP	Streak	Attempts	Hints	Last active	Status

Event queue (the sync-queue spine — every action is an append-only event)

Time	Event	Student	Payload	Synced

In production this is a SQLite event_queue table on the per-school box, flushed up via an idempotent, last-write-wins sync (see db/schema.sql).