fix(datasync): add guards and exception safety to JsonZstdFileSource

NEW/src/JdeScoping.DataSync/Etl/Sources/JsonZstdFileSource.cs

@@ -32,12 +32,29 @@ public sealed class JsonZstdFileSource : IImportSource
 
     public Task<IDataReader> ReadDataAsync(CancellationToken cancellationToken = default)
     {
-        _fileStream = new FileStream(_filePath, FileMode.Open, FileAccess.Read, FileShare.Read,
+        if (_fileStream != null)
-            bufferSize: 65536, useAsync: true);
+            throw new InvalidOperationException("ReadDataAsync has already been called. Dispose and create a new source to read again.");
-        _decompressionStream = new DecompressionStream(_fileStream);
-        _reader = new JsonStreamingDataReader(_decompressionStream, _schema);
 
-        return Task.FromResult<IDataReader>(_reader);
+        try
+        {
+            _fileStream = new FileStream(_filePath, FileMode.Open, FileAccess.Read, FileShare.Read,
+                bufferSize: 65536, useAsync: true);
+            _decompressionStream = new DecompressionStream(_fileStream);
+            _reader = new JsonStreamingDataReader(_decompressionStream, _schema);
+
+            return Task.FromResult<IDataReader>(_reader);
+        }
+        catch
+        {
+            // Clean up on failure
+            _reader?.Dispose();
+            _decompressionStream?.Dispose();
+            _fileStream?.Dispose();
+            _reader = null;
+            _decompressionStream = null;
+            _fileStream = null;
+            throw;
+        }
     }
 
     public async ValueTask DisposeAsync()