fix: persist empty POST in TR-069 trace when CPE uses a new TCP port

When a CPE sends an empty POST (polling) on a new TCP connection, the
remoteKey (IP:port) differs from the one registered during Inform.
Add StateMachineManager.getHashIdForRemoteIp() to find the device by
IP alone as a fallback, so cwmpDeviceId is resolved and the exchange
is properly stored in the trace (cwmpMethod: Empty, dashed arrow).

app/controllers/cwmp_controller.ts

@@ -40,7 +40,10 @@ export default class CwmpController {
     try {
       if (isEmpty) {
         const rebound = manager.ensureSessionForRemote(remoteKey, sessionId)
+        // Try exact remoteKey first (same TCP connection), then fall back to IP-only
+        // (CPE may open a new TCP port for the empty POST)
         const hashId = manager.getHashIdForRemote(remoteKey)
+          ?? manager.getHashIdForRemoteIp(request.ip())
         if (hashId) ctx.cwmpDeviceId = hashId
 
         logger.debug(