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_keypair.dart

@@ -44,7 +44,7 @@ class PushKeypair {
   final FlutterSecureStorageLike _storage;
 
   const PushKeypair({FlutterSecureStorageLike? storage})
-    : _storage = storage ?? const _DefaultStorage();
+    : _storage = storage ?? const PushSecureStorage();
 
   /// Returns the stored keypair PEMs, generating and persisting a fresh keypair
   /// on first use. Generation is offloaded to an isolate because RSA-2048 key
@@ -79,27 +79,3 @@ class PushKeypair {
     return PushKeypairPems(privateKeyPem: priv, publicKeyPem: pub);
   }
 }
-
-/// 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});
-}
-
-class _DefaultStorage implements FlutterSecureStorageLike {
-  const _DefaultStorage();
-
-  @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);
-}