Support AGH without DHCP server

lib/screens/settings/dhcp/dhcp_not_available.dart

@@ -0,0 +1,47 @@
+import 'package:flutter/material.dart';
+import 'package:flutter_gen/gen_l10n/app_localizations.dart';
+
+import 'package:adguard_home_manager/functions/desktop_mode.dart';
+
+class DhcpNotAvailable extends StatelessWidget {
+  const DhcpNotAvailable({super.key});
+
+  @override
+  Widget build(BuildContext context) {
+    final width = MediaQuery.of(context).size.width;
+
+    return Scaffold(
+      appBar: AppBar(
+        title: Text(AppLocalizations.of(context)!.dhcpSettings),
+        centerTitle: false,
+        surfaceTintColor: isDesktop(width) ? Colors.transparent : null,
+      ),
+      body: Padding(
+        padding: const EdgeInsets.all(16),
+        child: Column(
+          mainAxisAlignment: MainAxisAlignment.center,
+          children: [
+            Text(
+              AppLocalizations.of(context)!.dhcpNotAvailable,
+              textAlign: TextAlign.center,
+              style: const TextStyle(
+                fontWeight: FontWeight.w400,
+                fontSize: 24
+              ),
+            ),
+            const SizedBox(height: 20),
+             Text(
+              AppLocalizations.of(context)!.osServerInstalledIncompatible,
+              textAlign: TextAlign.center,
+              style: TextStyle(
+                fontWeight: FontWeight.w700,
+                fontSize: 16,
+                color: Theme.of(context).colorScheme.onSurfaceVariant
+              ),
+            ),
+          ],
+        ),
+      ),
+    );
+  }
+}