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

app/api/admin/validate-db/route.ts

@@ -0,0 +1,48 @@
+/**
+ * Manual Database Validation Endpoint
+ * 
+ * GET /api/admin/validate-db
+ * 
+ * Triggers immediate validation of database vs Drift positions
+ * Useful for debugging or manual checks
+ */
+
+import { NextRequest, NextResponse } from 'next/server'
+import { runManualValidation } from '@/lib/database/sync-validator'
+
+export async function GET(request: NextRequest) {
+  try {
+    // Optional: Add auth check
+    const authHeader = request.headers.get('authorization')
+    const expectedAuth = `Bearer ${process.env.API_SECRET_KEY}`
+    
+    if (authHeader && authHeader !== expectedAuth) {
+      return NextResponse.json(
+        { success: false, error: 'Unauthorized' },
+        { status: 401 }
+      )
+    }
+
+    console.log('🔧 Manual database validation triggered via API')
+    
+    const result = await runManualValidation()
+    
+    return NextResponse.json({
+      success: true,
+      result,
+      message: result.ghosts > 0 || result.orphans > 0
+        ? `Fixed ${result.ghosts} ghost(s) and ${result.orphans} orphan(s)`
+        : 'All trades validated successfully'
+    })
+
+  } catch (error) {
+    console.error('❌ Manual validation failed:', error)
+    return NextResponse.json(
+      {
+        success: false,
+        error: error instanceof Error ? error.message : 'Validation failed'
+      },
+      { status: 500 }
+    )
+  }
+}