add back client parameter for testing

mobile/lib/infrastructure/repositories/sync_api.repository.dart

@@ -25,8 +25,10 @@ class SyncApiRepository {
     Future<void> Function(List<SyncEvent>, Function() abort, Function() reset) onData, {
     Function()? onReset,
     int batchSize = kSyncEventBatchSize,
+    http.Client? httpClient,
   }) async {
     final stopwatch = Stopwatch()..start();
+    final client = httpClient ?? _client;
     final endpoint = "${_api.apiClient.basePath}/sync/stream";
 
     final headers = {'Content-Type': 'application/json', 'Accept': 'application/jsonlines+json'};
@@ -78,7 +80,7 @@ class SyncApiRepository {
     final reset = onReset ?? () {};
 
     try {
-      final response = await _client.send(request);
+      final response = await client.send(request);
 
       if (response.statusCode != 200) {
         final errorBody = await response.stream.bytesToString();

mobile/test/infrastructure/repositories/sync_api_repository_test.dart

@@ -118,7 +118,6 @@ void main() {
     expect(onDataCallCount, 1);
     expect(abortWasCalledInCallback, isTrue);
     expect(receivedEventsBatch1.length, testBatchSize);
-    verify(() => mockHttpClient.close()).called(1);
   });
 
   test('streamChanges does not process remaining lines in finally block if aborted', () async {
@@ -159,7 +158,6 @@ void main() {
 
     expect(onDataCallCount, 1);
     expect(abortWasCalledInCallback, isTrue);
-    verify(() => mockHttpClient.close()).called(1);
   });
 
   test('streamChanges processes remaining lines in finally block if not aborted', () async {
@@ -204,7 +202,6 @@ void main() {
     expect(onDataCallCount, 2);
     expect(receivedEventsBatch1.length, testBatchSize);
     expect(receivedEventsBatch2.length, 1);
-    verify(() => mockHttpClient.close()).called(1);
   });
 
   test('streamChanges handles stream error gracefully', () async {
@@ -229,7 +226,6 @@ void main() {
     await expectLater(streamChangesFuture, throwsA(streamError));
 
     expect(onDataCallCount, 0);
-    verify(() => mockHttpClient.close()).called(1);
   });
 
   test('streamChanges throws ApiException on non-200 status code', () async {
@@ -257,6 +253,5 @@ void main() {
     );
 
     expect(onDataCallCount, 0);
-    verify(() => mockHttpClient.close()).called(1);
   });
 }