User caught the inconsistency: system claims DB-first but price events
only went to price_events.json, leaving DB table stale since Jul 6.
Root cause chain found:
- record_event() only wrote JSON, never called mofin_db.write_price_event
- price_events.code has FK -> stocks(code); events for unregistered stocks
(new candidates, HK) silently failed INSERT and were lost to DB
- mofin_db.write_price_event swallows errors (returns False silently)
Fixes:
- record_event now dual-writes: DB (authoritative) + JSON (compat for
legacy readers mo_config/strategy_feedback/system_health_check)
- auto-registers unknown codes into stocks table before event insert
- one-time backfill: 4064 JSON events -> DB (total 6353 rows, last=today)
- verified: record_event TEST99 lands in both DB and JSON
