fix: Use Drift's actual entry price for breakeven SL

Problem: After TP1, SL moved to 'breakeven' but used database entry price,
which can differ from Drift's actual fill price by /bin/bash.10-0.15.

Example:
- DB stored: $139.18291 entry
- Drift actual: $139.07 entry
- SL set to: $139.18 (DB value)

Solution: Query position.entryPrice from Drift SDK when setting breakeven SL.
Drift SDK calculates entry from on-chain data (quoteAssetAmount / baseAssetAmount)
which is more accurate than database stored value.

Code change (lib/trading/position-manager.ts line ~511):
- Before: trade.stopLossPrice = trade.entryPrice
- After: trade.stopLossPrice = position.entryPrice || trade.entryPrice

Impact: TRUE breakeven protection - no slippage losses from price discrepancies.

Related: Common Pitfall #33 (orphaned position restoration with wrong entry price)

lib/trading/position-manager.ts

@@ -508,8 +508,13 @@ export class PositionManager {
             trade.tp1Hit = true
             trade.currentSize = positionSizeUSD
             
-            // Move SL to breakeven after TP1
-            trade.stopLossPrice = trade.entryPrice
+            // CRITICAL: Query Drift for ACTUAL entry price (more accurate than database)
+            // The position.entryPrice from Drift SDK is calculated from on-chain data
+            const actualEntryPrice = position.entryPrice || trade.entryPrice
+            console.log(`📊 Breakeven calculation: DB entry=$${trade.entryPrice.toFixed(4)}, Drift entry=$${actualEntryPrice.toFixed(4)}`)
+            
+            // Move SL to TRUE breakeven after TP1
+            trade.stopLossPrice = actualEntryPrice
             trade.slMovedToBreakeven = true
             console.log(`🛡️ Stop loss moved to breakeven: $${trade.stopLossPrice.toFixed(4)}`)