Add pagination to the devices list screen

Mirror the notifications list paging pattern (offset/limit, fetch one
extra row to detect the next page, First/Prev/Next controls) across the
devices DB query, REST endpoint, API client and UI. Also add a First
page button to the notifications pagination row.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

frontend/lib/utils/oott_api.dart

@@ -99,6 +99,8 @@ class BackendAPI {
     bool? isRegistered,
     String? owner,
     DeviceType? deviceType,
+    int? offset,
+    int? limit,
   }) async {
     debugPrint('About to call /devices');
 
@@ -110,6 +112,10 @@ class BackendAPI {
           ? ''
           : deviceType.apiName;
     }
+    if (offset != null) {
+      params['page_offset'] = offset;
+      params['page_limit'] = limit ?? _pageSize;
+    }
 
     final response = await _dio.get('/devices', queryParameters: params);