FINAL FIX: Docker API URL resolution for internal service communication

- Fixed internal API calls in Docker environment to use port 3000 instead of 9000
- Added DOCKER_ENV detection to properly route internal fetch requests
- Resolves ECONNREFUSED errors when APIs try to call each other within container
- Trade validation now works correctly in Docker: 5 USD position validates properly
- Successfully tested: amountUSD field properly passed through validation pipeline
- Both development and Docker environments now fully functional

app/api/trading/validate/route.js

@@ -7,10 +7,10 @@ export async function POST(request) {
 
     console.log(`🔍 Validating trade: ${side} ${amount} ${symbol} (USD: ${amountUSD})`)
 
-    // Get the base URL from the request or use localhost for development
+    // For Docker environment, use internal port 3000. For dev, use the host header
     const host = request.headers.get('host') || 'localhost:3000'
-    const protocol = host.includes('localhost') ? 'http' : 'https'
-    const baseUrl = `${protocol}://${host}`
+    const isDocker = process.env.DOCKER_ENV === 'true'
+    const baseUrl = isDocker ? 'http://localhost:3000' : `http://${host}`
 
     // Fetch real wallet balance from the wallet API
     let walletBalance