fix(smartproxy): improve certificate manager mocking in tests, enhance IPv6 validation, and record initial bytes for connection metrics

ts/proxies/smart-proxy/route-connection-handler.ts

@@ -1490,6 +1490,12 @@ export class RouteConnectionHandler {
             );
           }
 
+          // Record the initial chunk bytes for metrics
+          record.bytesReceived += combinedData.length;
+          if (this.smartProxy.metricsCollector) {
+            this.smartProxy.metricsCollector.recordBytes(record.id, combinedData.length, 0);
+          }
+
           // Write pending data immediately
           targetSocket.write(combinedData, (err) => {
             if (err) {