fix(trader): separate stop-loss and take-profit order cancellation to prevent accidental deletions

## Problem
When adjusting stop-loss or take-profit levels, `CancelStopOrders()` deleted BOTH stop-loss AND take-profit orders simultaneously, causing:
- **Adjusting stop-loss** → Take-profit order deleted → Position has no exit plan ❌
- **Adjusting take-profit** → Stop-loss order deleted → Position unprotected ❌

**Root cause:**
```go
CancelStopOrders(symbol) {
  // Cancelled ALL orders with type STOP_MARKET or TAKE_PROFIT_MARKET
  // No distinction between stop-loss and take-profit
}
```

## Solution

### 1. Added new interface methods (trader/interface.go)
```go
CancelStopLossOrders(symbol string) error      // Only cancel stop-loss orders
CancelTakeProfitOrders(symbol string) error    // Only cancel take-profit orders
CancelStopOrders(symbol string) error          // Deprecated (cancels both)
```

### 2. Implemented for all 3 exchanges

**Binance (trader/binance_futures.go)**:
- `CancelStopLossOrders`: Filters `OrderTypeStopMarket | OrderTypeStop`
- `CancelTakeProfitOrders`: Filters `OrderTypeTakeProfitMarket | OrderTypeTakeProfit`
- Full order type differentiation ✅

**Hyperliquid (trader/hyperliquid_trader.go)**:
- ⚠️ Limitation: SDK's OpenOrder struct doesn't expose trigger field
- Both methods call `CancelStopOrders` (cancels all pending orders)
- Trade-off: Safe but less precise

**Aster (trader/aster_trader.go)**:
- `CancelStopLossOrders`: Filters `STOP_MARKET | STOP`
- `CancelTakeProfitOrders`: Filters `TAKE_PROFIT_MARKET | TAKE_PROFIT`
- Full order type differentiation ✅

### 3. Usage in auto_trader.go
When `update_stop_loss` or `update_take_profit` actions are implemented, they will use:
```go
// update_stop_loss:
at.trader.CancelStopLossOrders(symbol)  // Only cancel SL, keep TP
at.trader.SetStopLoss(...)

// update_take_profit:
at.trader.CancelTakeProfitOrders(symbol)  // Only cancel TP, keep SL
at.trader.SetTakeProfit(...)
```

## Impact
- ✅ Adjusting stop-loss no longer deletes take-profit
- ✅ Adjusting take-profit no longer deletes stop-loss
- ✅ Backward compatible: `CancelStopOrders` still exists (deprecated)
- ⚠️ Hyperliquid limitation: still cancels all orders (SDK constraint)

## Testing
- ✅ Compiles successfully across all 3 exchanges
- ⚠️ Requires live testing:
  - [ ] Binance: Adjust SL → verify TP remains
  - [ ] Binance: Adjust TP → verify SL remains
  - [ ] Hyperliquid: Verify behavior with limitation
  - [ ] Aster: Verify order filtering works correctly

## Code Changes
```
trader/interface.go: +9 lines (new interface methods)
trader/binance_futures.go: +133 lines (3 new functions)
trader/hyperliquid_trader.go: +56 lines (3 new functions)
trader/aster_trader.go: +157 lines (3 new functions)
Total: +355 lines
```

trader/interface.go

@@ -36,6 +36,16 @@ type Trader interface {
 	// SetTakeProfit 设置止盈单
 	SetTakeProfit(symbol string, positionSide string, quantity, takeProfitPrice float64) error
 
+	// CancelStopOrders 取消该币种的止盈/止损单（已废弃：会同时删除止损和止盈）
+	// 请使用 CancelStopLossOrders 或 CancelTakeProfitOrders
+	CancelStopOrders(symbol string) error
+
+	// CancelStopLossOrders 仅取消止损单（修复 BUG：调整止损时不删除止盈）
+	CancelStopLossOrders(symbol string) error
+
+	// CancelTakeProfitOrders 仅取消止盈单（修复 BUG：调整止盈时不删除止损）
+	CancelTakeProfitOrders(symbol string) error
+
 	// CancelAllOrders 取消该币种的所有挂单
 	CancelAllOrders(symbol string) error