chore: Linter fixes for USB serial transport

lib/services/serial/usb_serial_transport.dart

@@ -1,5 +1,4 @@
 import 'dart:async';
-import 'dart:typed_data';
 import 'package:flutter/foundation.dart';
 import 'package:usb_serial/usb_serial.dart';
 import 'package:meshcore_client/meshcore_client.dart';

lib/services/serial/web_serial_transport.dart

@@ -1,6 +1,4 @@
 import 'dart:async';
-import 'dart:typed_data';
-import 'package:flutter/foundation.dart';
 import 'package:meshcore_client/meshcore_client.dart';
 
 // Web Serial API is only available on web platform.

lib/widgets/connection_dialog.dart

@@ -758,6 +758,7 @@ class _UsbDeviceListState extends State<_UsbDeviceList> {
         widget.onConnected();
       } else {
         await port.close();
+        if (!mounted) return;
         setState(() => _isConnecting = false);
         ScaffoldMessenger.of(context).showSnackBar(
           const SnackBar(content: Text('Failed to connect via USB')),

pubspec.lock

@@ -1470,7 +1470,7 @@ packages:
     source: hosted
     version: "1.4.0"
   web:
-    dependency: transitive
+    dependency: "direct main"
     description:
       name: web
       sha256: "868d88a33d8a87b18ffc05f9f030ba328ffefba92d6c127917a2ba740f9cfe4a"

pubspec.yaml

@@ -122,6 +122,7 @@ dependencies:
   # Network Service Discovery (Bonjour/mDNS)
   nsd: ^4.0.3
   usb_serial: ^0.5.2
+  web: ^1.1.1
 
 dev_dependencies:
   flutter_test: