fix: ensure all timestamps use UTC timezone

- Add NowFunc to GORM config for UTC auto-generated timestamps
- Add .UTC() to all time.UnixMilli() calls in trader files
- Add .UTC() to all time.Now() calls in store and api files
- Fix TypeScript unused imports in frontend

trader/aster_trader.go

@@ -1407,7 +1407,7 @@ func (t *AsterTrader) GetTrades(startTime time.Time, limit int) ([]TradeRecord,
 			Quantity:     qty,
 			RealizedPnL:  pnl,
 			Fee:          fee,
-			Time:         time.UnixMilli(at.Time),
+			Time:         time.UnixMilli(at.Time).UTC(),
 		}
 		result = append(result, trade)
 	}