feat: Add automated database sync validator for ghost position detection

PROBLEM:
- Analytics page showed 3 open trades when only 1 actually open on Drift
- Ghost positions in database (realizedPnL set but exitReason = NULL)
- Happens when on-chain orders fill but database update fails
- Manual cleanup required = unreliable dashboard

SOLUTION: Automated Database Sync Validator
1. Runs every 10 minutes (independent of Position Manager)
2. Validates ALL 'open' database trades against actual Drift positions
3. Auto-fixes ghost positions (marks as closed with exitReason)
4. Provides manual validation endpoint: GET /api/admin/validate-db

FEATURES:
- Detects ghost positions (DB open, Drift closed)
- Detects orphan positions (DB closed, Drift open)
- Provides detailed validation reports
- Runs on server startup + periodic intervals
- Zero manual intervention required

FILES:
- lib/database/sync-validator.ts: Core validation logic
- app/api/admin/validate-db/route.ts: Manual validation endpoint
- instrumentation.ts: Auto-start on server initialization

RESULT: Reliable dashboard data - always matches Drift reality

instrumentation.ts

@@ -13,6 +13,10 @@ export async function register() {
     const { initializePositionManagerOnStartup } = await import('./lib/startup/init-position-manager')
     await initializePositionManagerOnStartup()
     
+    // Start database sync validator (runs every 10 minutes)
+    const { startDatabaseSyncValidator } = await import('./lib/database/sync-validator')
+    startDatabaseSyncValidator()
+    
     console.log('✅ Server initialization complete')
   }
 }