added support for simultan downloads in files and talk, support for background downloads, enhanced loading in files with retry

test/api/errors/error_mapper_test.dart

@@ -8,7 +8,9 @@ import 'package:marianum_mobile/api/api_error.dart';
 import 'package:marianum_mobile/api/errors/auth_exception.dart';
 import 'package:marianum_mobile/api/errors/error_mapper.dart';
 import 'package:marianum_mobile/api/errors/network_exception.dart';
+import 'package:marianum_mobile/api/errors/not_found_exception.dart';
 import 'package:marianum_mobile/api/errors/parse_exception.dart';
+import 'package:nextcloud/nextcloud.dart';
 
 void main() {
   group('errorToUserMessage', () {
@@ -95,7 +97,7 @@ void main() {
       expect(errorToUserMessage(ex), const NetworkException().userMessage);
     });
 
-    test('DioException badResponse maps to a server status message', () {
+    test('DioException badResponse maps to the server error message', () {
       final ex = DioException(
         requestOptions: RequestOptions(path: '/x'),
         type: DioExceptionType.badResponse,
@@ -104,7 +106,65 @@ void main() {
           statusCode: 503,
         ),
       );
-      expect(errorToUserMessage(ex), contains('503'));
+      // The status code lives in the technical details, not the message.
+      expect(
+        errorToUserMessage(ex),
+        contains('konnte die Anfrage gerade nicht verarbeiten'),
+      );
+      expect(errorToTechnicalDetails(ex), contains('503'));
+    });
+  });
+
+  group('DynamiteApiException mapping', () {
+    test('500 maps to the server error message without the raw dump', () {
+      const ex = DynamiteApiException(500, {'server': 'nginx'}, '');
+      expect(
+        errorToUserMessage(ex),
+        contains('konnte die Anfrage gerade nicht verarbeiten'),
+      );
+      expect(errorToTechnicalDetails(ex), 'HTTP 500');
+      expect(errorToTechnicalDetails(ex), isNot(contains('nginx')));
+      expect(errorAllowsRetry(ex), isTrue);
+    });
+
+    test('5xx details include a trimmed body preview', () {
+      const ex = DynamiteApiException(503, {}, '  Service\n  Unavailable  ');
+      expect(errorToTechnicalDetails(ex), 'HTTP 503 body=Service Unavailable');
+    });
+
+    test('long bodies are capped in the details', () {
+      final ex = DynamiteApiException(502, const {}, 'x' * 600);
+      final details = errorToTechnicalDetails(ex)!;
+      expect(details, startsWith('HTTP 502 body='));
+      expect(details, endsWith('…'));
+      expect(details.length, lessThan(600));
+    });
+
+    test('401 maps to the unauthorized AuthException', () {
+      const ex = DynamiteApiException(401, {}, '');
+      expect(
+        errorToUserMessage(ex),
+        AuthException.unauthorized().userMessage,
+      );
+      expect(errorAllowsRetry(ex), isFalse);
+    });
+
+    test('403 maps to the forbidden AuthException', () {
+      const ex = DynamiteApiException(403, {}, '');
+      expect(errorToUserMessage(ex), AuthException.forbidden().userMessage);
+      expect(errorAllowsRetry(ex), isFalse);
+    });
+
+    test('404 maps to NotFoundException', () {
+      const ex = DynamiteApiException(404, {}, '');
+      expect(errorToUserMessage(ex), const NotFoundException().userMessage);
+      expect(errorAllowsRetry(ex), isFalse);
+    });
+
+    test('429 maps to a rate-limit message that allows retry', () {
+      const ex = DynamiteApiException(429, {}, '');
+      expect(errorToUserMessage(ex), contains('Zu viele Anfragen'));
+      expect(errorAllowsRetry(ex), isTrue);
     });
   });