- one-time import from the legacy JSON (left in place as snapshot);
ghost rows (int vs str ep_id) deduped on import, unrepresentable after
- history POST is now an upsert: the (user, slug_id, ep_id) PK is the
merge key, so the unguarded read-modify-write (lost updates) and the
corruption-swallow (JSONDecodeError -> [] -> fresh overwrite) are gone
- searches: NOCASE PK upsert + cap 8
- events table + position/search logging (watch-time trajectory),
90-day retention pruned at boot
- account delete cascades all four tables
- 22/22 tests green; old JSON files untouched
