fix(sync): use actual trade time instead of current time for lastSyncTime

- Remove syncStartTimeMs that was causing sync gaps
- Update binanceSyncState to latest trade's timestamp after successful sync
- Don't update lastSyncTime when no trades found (keep using DB value)

Fixes issue where trades between last sync and current time were missed

trader/binance_order_sync.go

@@ -56,10 +56,6 @@ func (t *FuturesTrader) SyncOrdersFromBinance(traderID string, exchangeID string
 		}
 	}
 
-	// Record current time BEFORE querying, to avoid missing trades during sync
-	// This prevents race condition where trades happen between query and lastSyncTime update
-	syncStartTimeMs := nowMs
-
 	logger.Infof("🔄 Syncing Binance trades from: %s (UTC) [ms: %d, now: %d]",
 		time.UnixMilli(lastSyncTimeMs).UTC().Format("2006-01-02 15:04:05"), lastSyncTimeMs, nowMs)
 
@@ -121,10 +117,9 @@ func (t *FuturesTrader) SyncOrdersFromBinance(traderID string, exchangeID string
 
 	if len(changedSymbols) == 0 {
 		logger.Infof("📭 No symbols with new trades to sync")
-		// Update last sync time even if no changes
+		// DON'T update lastSyncTime to current time here!
-		binanceSyncStateMutex.Lock()
+		// Keep using the last actual trade time from DB to avoid creating gaps
-		binanceSyncState[exchangeID] = syncStartTimeMs
+		// The lastSyncTimeMs from DB already has +1000ms buffer added
-		binanceSyncStateMutex.Unlock()
 		return nil
 	}
 
@@ -157,17 +152,12 @@ func (t *FuturesTrader) SyncOrdersFromBinance(traderID string, exchangeID string
 
 	logger.Infof("📥 Received %d trades from Binance (%d API calls)", len(allTrades), apiCalls)
 
-	// Only update last sync time if ALL symbols were successfully queried
-	// This prevents data loss when some symbols fail due to rate limit or network issues
-	if len(failedSymbols) == 0 {
-		binanceSyncStateMutex.Lock()
-		binanceSyncState[exchangeID] = syncStartTimeMs
-		binanceSyncStateMutex.Unlock()
-	} else {
-		logger.Infof("  ⚠️ %d symbols failed, not updating lastSyncTime to retry next time: %v", len(failedSymbols), failedSymbols)
-	}
-
 	if len(allTrades) == 0 {
+		// No trades returned, but symbols were detected - might be false positive from COMMISSION/PnL detection
+		// Don't update lastSyncTime, keep using DB value
+		if len(failedSymbols) > 0 {
+			logger.Infof("  ⚠️ %d symbols failed: %v", len(failedSymbols), failedSymbols)
+		}
 		return nil
 	}
 
@@ -281,6 +271,20 @@ func (t *FuturesTrader) SyncOrdersFromBinance(traderID string, exchangeID string
 			trade.Time.UTC().Format("01-02 15:04:05"))
 	}
 
+	// Update lastSyncTime to the LATEST trade time (not current time!)
+	// This ensures next sync starts from where we left off, not from "now"
+	// allTrades is already sorted by time ASC, so last element is the latest
+	if len(allTrades) > 0 && len(failedSymbols) == 0 {
+		latestTradeTimeMs := allTrades[len(allTrades)-1].Time.UTC().UnixMilli()
+		binanceSyncStateMutex.Lock()
+		binanceSyncState[exchangeID] = latestTradeTimeMs
+		binanceSyncStateMutex.Unlock()
+		logger.Infof("📅 Updated lastSyncTime to latest trade: %s (UTC)",
+			time.UnixMilli(latestTradeTimeMs).UTC().Format("2006-01-02 15:04:05"))
+	} else if len(failedSymbols) > 0 {
+		logger.Infof("  ⚠️ %d symbols failed, not updating lastSyncTime to retry next time: %v", len(failedSymbols), failedSymbols)
+	}
+
 	logger.Infof("✅ Binance order sync completed: %d new trades synced, %d skipped (already exist)", syncedCount, skippedCount)
 	return nil
 }