critical: Bug #93 - Three-layer entry price validation with oracle fallback

Root Cause: quoteAssetAmount/baseAssetAmount division producing garbage entry prices
- Found 6 autosync records with impossible prices (.18, 6.30, 7.11, 116.24 for SOL)
- Drift SDK values can be corrupted during state transitions

Fix Layer 1 (lib/drift/client.ts):
- Added per-asset price range validation (SOL: 0-000, BTC: 0k-00k, ETH: 00-0k)
- Returns null for invalid prices

Fix Layer 2 (lib/trading/sync-helper.ts):
- Added validatedEntryPrice calculation with oracle fallback
- Falls back to Pyth oracle when calculated price is garbage

Fix Layer 3 (lib/trading/sync-helper.ts):
- Trade creation uses validatedEntryPrice in all 4 price fields
- entryPrice, peakPrice, maxFavorablePrice, maxAdversePrice

Documentation:
- Full Bug #93 added to COMMON_PITFALLS.md with code examples
- Quick Reference table updated

Cleaned: 6 garbage autosync records deleted from database

lib/trading/sync-helper.ts

@@ -107,7 +107,31 @@ export async function syncSinglePosition(driftPos: any, positionManager: any): P
     const direction = driftPos.side
     const entryPrice = driftPos.entryPrice
     
-    // Calculate TP/SL prices
+    // BUG #89 FIX: Validate entry price is realistic before creating sync record
+    // Prevents garbage autosync records with impossible entry prices
+    const priceValidation: { [symbol: string]: { min: number; max: number } } = {
+      'SOL-PERP': { min: 50, max: 1000 },    // SOL: $50-$1000 range
+      'BTC-PERP': { min: 10000, max: 500000 }, // BTC: $10k-$500k range
+      'ETH-PERP': { min: 500, max: 20000 },   // ETH: $500-$20k range
+    }
+    
+    const validation = priceValidation[driftPos.symbol]
+    if (validation && (entryPrice < validation.min || entryPrice > validation.max)) {
+      console.error(`❌ AUTOSYNC REJECTED: Invalid entry price $${entryPrice.toFixed(2)} for ${driftPos.symbol}`)
+      console.error(`   Expected range: $${validation.min}-$${validation.max}`)
+      console.error(`   Current oracle price: $${currentPrice.toFixed(2)}`)
+      console.error(`   Position size: ${driftPos.size} tokens`)
+      console.error(`   Using oracle price as fallback entry price`)
+      // Use oracle price as fallback instead of garbage entry price
+      // This is acceptable for syncing since we're just trying to track the position
+    }
+    
+    // Use validated entry price (fallback to oracle if garbage)
+    const validatedEntryPrice = (validation && (entryPrice < validation.min || entryPrice > validation.max)) 
+      ? currentPrice 
+      : entryPrice
+    
+    // Calculate TP/SL prices using validated entry
     const calculatePrice = (entry: number, percent: number, dir: 'long' | 'short') => {
       if (dir === 'long') {
         return entry * (1 + percent / 100)
@@ -116,10 +140,10 @@ export async function syncSinglePosition(driftPos: any, positionManager: any): P
       }
     }
     
-    const stopLossPrice = calculatePrice(entryPrice, config.stopLossPercent, direction)
-    const tp1Price = calculatePrice(entryPrice, config.takeProfit1Percent, direction)
-    const tp2Price = calculatePrice(entryPrice, config.takeProfit2Percent, direction)
-    const emergencyStopPrice = calculatePrice(entryPrice, config.emergencyStopPercent, direction)
+    const stopLossPrice = calculatePrice(validatedEntryPrice, config.stopLossPercent, direction)
+    const tp1Price = calculatePrice(validatedEntryPrice, config.takeProfit1Percent, direction)
+    const tp2Price = calculatePrice(validatedEntryPrice, config.takeProfit2Percent, direction)
+    const emergencyStopPrice = calculatePrice(validatedEntryPrice, config.emergencyStopPercent, direction)
 
     // Calculate position size in USD (Drift size is tokens)
     const positionSizeUSD = Math.abs(driftPos.size) * currentPrice
@@ -286,7 +310,7 @@ export async function syncSinglePosition(driftPos: any, positionManager: any): P
           positionId: syntheticPositionId,
           symbol: driftPos.symbol,
           direction,
-          entryPrice,
+          entryPrice: validatedEntryPrice,  // BUG #89 FIX: Use validated entry price
           entryTime: now,
           positionSizeUSD,
           collateralUSD: positionSizeUSD / config.leverage,
@@ -323,12 +347,12 @@ export async function syncSinglePosition(driftPos: any, positionManager: any): P
               realizedPnL: 0,
               unrealizedPnL: driftPos.unrealizedPnL ?? 0,
               peakPnL: driftPos.unrealizedPnL ?? 0,
-              peakPrice: entryPrice,
+              peakPrice: validatedEntryPrice,  // BUG #89 FIX: Use validated entry price
               lastPrice: currentPrice,
               maxFavorableExcursion: 0,
               maxAdverseExcursion: 0,
-              maxFavorablePrice: entryPrice,
-              maxAdversePrice: entryPrice,
+              maxFavorablePrice: validatedEntryPrice,  // BUG #89 FIX: Use validated entry price
+              maxAdversePrice: validatedEntryPrice,    // BUG #89 FIX: Use validated entry price
               lastUpdate: now.toISOString(),
               // TP2 runner configuration (CRITICAL FIX - Dec 12, 2025)
               tp1SizePercent: config.takeProfit1SizePercent,