feat: Add phantom trade detection and database tracking

- Detect position size mismatches (>50% variance) after opening
- Save phantom trades to database with expectedSizeUSD, actualSizeUSD, phantomReason
- Return error from execute endpoint to prevent Position Manager tracking
- Add comprehensive documentation of phantom trade issue and solution
- Enable data collection for pattern analysis and future optimization

Fixes oracle price lag issue during volatile markets where transactions
confirm but positions don't actually open at expected size.

prisma/schema.prisma

@@ -103,9 +103,15 @@ model Trade {
   timeframe        String?  // "5", "15", "60"
   
   // Status
-  status           String   @default("open") // "open", "closed", "failed"
+  status           String   @default("open") // "open", "closed", "failed", "phantom"
   isTestTrade      Boolean  @default(false) // Flag test trades for exclusion from analytics
   
+  // Phantom trade detection
+  isPhantom        Boolean  @default(false) // Position opened but size mismatch >50%
+  expectedSizeUSD  Float?   // Expected position size (when phantom)
+  actualSizeUSD    Float?   // Actual position size from Drift (when phantom)
+  phantomReason    String?  // "ORACLE_PRICE_MISMATCH", "PARTIAL_FILL", "ORDER_REJECTED"
+  
   // Relations
   priceUpdates     PriceUpdate[]