refactor(ios): dedupe gateway helpers

apps/ios/Sources/Model/NodeAppModel+Canvas.swift

@@ -61,37 +61,10 @@ extension NodeAppModel {
     private static func probeTCP(url: URL, timeoutSeconds: Double) async -> Bool {
         guard let host = url.host, !host.isEmpty else { return false }
         let portInt = url.port ?? ((url.scheme ?? "").lowercased() == "wss" ? 443 : 80)
-        guard portInt >= 1, portInt <= 65535 else { return false }
-        guard let nwPort = NWEndpoint.Port(rawValue: UInt16(portInt)) else { return false }
-
-        let endpointHost = NWEndpoint.Host(host)
-        let connection = NWConnection(host: endpointHost, port: nwPort, using: .tcp)
-        return await withCheckedContinuation { cont in
-            let queue = DispatchQueue(label: "a2ui.preflight")
-            let finished = OSAllocatedUnfairLock(initialState: false)
-            let finish: @Sendable (Bool) -> Void = { ok in
-                let shouldResume = finished.withLock { flag -> Bool in
-                    if flag { return false }
-                    flag = true
-                    return true
-                }
-                guard shouldResume else { return }
-                connection.cancel()
-                cont.resume(returning: ok)
-            }
-
-            connection.stateUpdateHandler = { state in
-                switch state {
-                case .ready:
-                    finish(true)
-                case .failed, .cancelled:
-                    finish(false)
-                default:
-                    break
-                }
-            }
-            connection.start(queue: queue)
-            queue.asyncAfter(deadline: .now() + timeoutSeconds) { finish(false) }
-        }
+        return await TCPProbe.probe(
+            host: host,
+            port: portInt,
+            timeoutSeconds: timeoutSeconds,
+            queueLabel: "a2ui.preflight")
     }
 }