implemented a 1-minute in-memory cache for the EmergencyNoticeClient to prevent redundant network requests on app resume

lib/api/emergency/emergency_notice_client.dart

@@ -2,17 +2,30 @@ import 'package:dio/dio.dart';
 
 import 'emergency_notice.dart';
 
-/// Loads the emergency notice from a foreign URL over a standalone [Dio]
-/// instance — no MarianumConnect interceptors, base URL or auth. That keeps the
-/// fallback fully independent of the backend it is meant to survive.
+/// Loads the emergency notice from a foreign URL over a standalone [Dio] — no
+/// MarianumConnect interceptors/base URL/auth, so it survives a backend outage.
+/// Never throws: any failure yields `null` (nothing shown).
 ///
-/// Fail-safe by contract: if the server is unreachable, times out, answers with
-/// a non-2xx status or delivers unparsable content, [fetch] returns `null` and
-/// nothing is shown. It never throws.
+/// A [cacheTtl] in-memory throttle keeps rapid resumes from hammering the host;
+/// it lives only for the process, so a cold start always fetches fresh.
 class EmergencyNoticeClient {
-  const EmergencyNoticeClient();
+  EmergencyNoticeClient();
+
+  static const Duration cacheTtl = Duration(minutes: 1);
+
+  EmergencyNotice? _cached;
+  String? _cachedUrl;
+  DateTime? _cachedAt;
 
   Future<EmergencyNotice?> fetch(String url) async {
+    final cachedAt = _cachedAt;
+    if (cachedAt != null &&
+        _cachedUrl == url &&
+        DateTime.now().difference(cachedAt) < cacheTtl) {
+      return _cached;
+    }
+
+    EmergencyNotice? result;
     try {
       final dio = Dio(
         BaseOptions(
@@ -24,11 +37,15 @@ class EmergencyNoticeClient {
       );
       final response = await dio.get<String>(url);
       final raw = response.data;
-      if (raw == null || raw.isEmpty) return null;
-      return EmergencyNotice.parse(raw);
+      result = (raw == null || raw.isEmpty) ? null : EmergencyNotice.parse(raw);
     } catch (_) {
-      // Server down / timeout / bad status / malformed body: show nothing.
-      return null;
+      result = null;
     }
+
+    // Cache failures too, so a down server isn't retried on every resume.
+    _cached = result;
+    _cachedUrl = url;
+    _cachedAt = DateTime.now();
+    return result;
   }
 }