修复 scale-in 后 leg.EntryPrice 不更新 + 重启恢复时加载 scale prices

- trader.go: scale-in 后用 weightedAvgPrice 更新 LongLeg/ShortLeg.EntryPrice
- trader.go: restoreOpenPositions 从 orders 表加载 scale prices 重建完整价格切片
- db/trade_repo.go: 新增 GetScalePrices(tradeID) 方法
- README: v1.2.1 版本记录

trader.go

@@ -547,6 +547,10 @@ func (t *Trader) checkScaleIn(pos *ArbPosition, bgP, hlP, diffPct float64, store
 	pos.LongEntryPrices = append(pos.LongEntryPrices, longPrice)
 	pos.ShortEntryPrices = append(pos.ShortEntryPrices, shortPrice)
 
+	// Update leg EntryPrice to reflect weighted average across all scale levels
+	pos.LongLeg.EntryPrice = weightedAvgPrice(pos.LongEntryPrices, t.cfg.TradeAmountUSD)
+	pos.ShortLeg.EntryPrice = weightedAvgPrice(pos.ShortEntryPrices, t.cfg.TradeAmountUSD)
+
 	// Persist scale orders to DB immediately
 	if t.db != nil && pos.DBTradeID > 0 {
 		now := time.Now()
@@ -1172,6 +1176,20 @@ func (t *Trader) restoreOpenPositions() {
 			}
 			pos.ShortEntryPrices = []float64{*tr.ShortEntry}
 		}
+
+		// Restore scale-in prices from orders table for correct weighted average
+		scaleLong, scaleShort, err := t.db.GetScalePrices(tr.ID)
+		if err == nil {
+			pos.LongEntryPrices = append(pos.LongEntryPrices, scaleLong...)
+			pos.ShortEntryPrices = append(pos.ShortEntryPrices, scaleShort...)
+			// Refresh leg EntryPrice to reflect all scale levels
+			if len(pos.LongEntryPrices) > 1 {
+				pos.LongLeg.EntryPrice = weightedAvgPrice(pos.LongEntryPrices, t.cfg.TradeAmountUSD)
+			}
+			if len(pos.ShortEntryPrices) > 1 {
+				pos.ShortLeg.EntryPrice = weightedAvgPrice(pos.ShortEntryPrices, t.cfg.TradeAmountUSD)
+			}
+		}
 		t.positions[tr.Coin] = pos
 		// Prevent immediate re-trading of the same coin
 		t.lastTradeTime[tr.Coin] = tr.OpenedAt