fix: leverage validation bug and limit grid leverage to 1-5

- Fix Go range loop copy issue in validateDecisions (leverage auto-adjust was modifying copy, not original)
- Limit grid leverage from 1-20 to 1-5 for safer grid trading

kernel/engine.go

@@ -1767,8 +1767,8 @@ func compactArrayOpen(s string) string {
 // ============================================================================
 
 func validateDecisions(decisions []Decision, accountEquity float64, btcEthLeverage, altcoinLeverage int, btcEthPosRatio, altcoinPosRatio float64) error {
-	for i, decision := range decisions {
-		if err := validateDecision(&decision, accountEquity, btcEthLeverage, altcoinLeverage, btcEthPosRatio, altcoinPosRatio); err != nil {
+	for i := range decisions {
+		if err := validateDecision(&decisions[i], accountEquity, btcEthLeverage, altcoinLeverage, btcEthPosRatio, altcoinPosRatio); err != nil {
 			return fmt.Errorf("decision #%d validation failed: %w", i+1, err)
 		}
 	}

web/src/components/strategy/GridConfigEditor.tsx

@@ -47,7 +47,7 @@ export function GridConfigEditor({
       totalInvestment: { zh: '投资金额 (USDT)', en: 'Investment (USDT)' },
       totalInvestmentDesc: { zh: '网格策略的总投资金额', en: 'Total investment for grid strategy' },
       leverage: { zh: '杠杆倍数', en: 'Leverage' },
-      leverageDesc: { zh: '交易使用的杠杆倍数 (1-20)', en: 'Leverage for trading (1-20)' },
+      leverageDesc: { zh: '交易使用的杠杆倍数 (1-5)', en: 'Leverage for trading (1-5)' },
 
       // Grid parameters
       gridCount: { zh: '网格数量', en: 'Grid Count' },
@@ -171,7 +171,7 @@ export function GridConfigEditor({
               onChange={(e) => updateField('leverage', parseInt(e.target.value) || 5)}
               disabled={disabled}
               min={1}
-              max={20}
+              max={5}
               className="w-full px-3 py-2 rounded"
               style={inputStyle}
             />