✨ Implement WebSocket API client

- List ports
- Read and write mute state
- Read and write volume

lib/error_page.dart

@@ -0,0 +1,32 @@
+import 'package:flutter/material.dart';
+
+class ErrorPage extends StatefulWidget {
+  final String message;
+  const ErrorPage({super.key, this.message = "Something went wrong!"});
+
+  @override
+  State<ErrorPage> createState() => _ErrorPageState();
+}
+
+class _ErrorPageState extends State<ErrorPage> {
+  @override
+  Widget build(BuildContext context) {
+    return Center(
+      child: Column(
+        crossAxisAlignment: CrossAxisAlignment.center,
+        mainAxisAlignment: MainAxisAlignment.center,
+        children: [
+          const Icon(
+            Icons.cloud_off_outlined,
+            size: 48,
+          ),
+          const SizedBox(height: 10),
+          Text(
+            widget.message,
+            style: const TextStyle(fontSize: 16),
+          )
+        ],
+      ),
+    );
+  }
+}