fix: cross-market signal deduplication in PostgreSQL aggregation #12
Description
Impact
Same event triggers signals from multiple sentinels, creating duplicate alerts.
Signal Source
Central meta-sentinel aggregation — overlapping market hours (HK/JP/crypto).
Expected
Dedup by (signal_type, symbol, 15min_window), highest confidence wins.
Blast Radius
Alert noise; no data loss. Over-notification to QQ/Telegram.
Rollback Plan
N/A — additive dedup logic, no destructive change.