implemented dual Nextcloud push registration with separate general and talk apptypes to ensure reliable Talk notification delivery; introduced stacked MessagingStyle notifications for chat threads with support for circular conversation avatars and disk caching

lib/push/push_secure_storage.dart

@@ -25,3 +25,28 @@ const IOSOptions kPushIosOptions = IOSOptions(
 const FlutterSecureStorage pushSecureStorage = FlutterSecureStorage(
   iOptions: kPushIosOptions,
 );
+
+/// Minimal storage contract so tests can inject an in-memory fake instead of
+/// touching the platform keystore.
+abstract class FlutterSecureStorageLike {
+  Future<String?> read({required String key});
+  Future<void> write({required String key, required String? value});
+  Future<void> delete({required String key});
+}
+
+/// Default [FlutterSecureStorageLike] backed by [pushSecureStorage].
+class PushSecureStorage implements FlutterSecureStorageLike {
+  const PushSecureStorage();
+
+  @override
+  Future<String?> read({required String key}) =>
+      pushSecureStorage.read(key: key);
+
+  @override
+  Future<void> write({required String key, required String? value}) =>
+      pushSecureStorage.write(key: key, value: value);
+
+  @override
+  Future<void> delete({required String key}) =>
+      pushSecureStorage.delete(key: key);
+}