Add DHCP scanner to frontend status displays

Add a DHCP scanner card to the Status screen and a DHCP row to the
consolidated Status card on the Home screen, mirroring the existing
mDNS/SSDP implementations. Also label DHCP-discovered device events as
"DHCP" instead of the raw "Dhcp".

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/lib/utils/oott_api.dart

@@ -7,6 +7,7 @@ import 'package:flutter/foundation.dart';
 import 'package:frontend/utils/backend_reachability.dart';
 import 'package:frontend/utils/pref_utils.dart';
 import '../model/arp_scanner_status.dart';
+import '../model/dhcp_scanner_status.dart';
 import '../model/mdns_scanner_status.dart';
 import '../model/ssdp_scanner_status.dart';
 import '../model/device.dart';
@@ -322,6 +323,16 @@ class BackendAPI {
     return SsdpScannerStatus.fromJson(response.data as Map<String, dynamic>);
   }
 
+  Future<DhcpScannerStatus> getDhcpScannerStatus({
+    CancelToken? cancelToken,
+  }) async {
+    final response = await _dio.get(
+      '/dhcp_scanner/status',
+      cancelToken: cancelToken,
+    );
+    return DhcpScannerStatus.fromJson(response.data as Map<String, dynamic>);
+  }
+
   Future<({List<Notification> items, bool hasNextPage})> listNotifications(
     bool? isNew, {
     int page = 0,