fix(ftp): close FTP client connection and protocol on all code paths

FTPDownloadHandler.download_request() creates an FTPClient via
ClientCreator.connectTCP() but never calls loseConnection(), leaking
the TCP connection. Additionally, the ReceivedDataProtocol is not
closed on the CommandFailed error path, leaking file handles or
memory buffers.

Move protocol.close() into a finally block and add
client.loseConnection() there so both resources are always cleaned
up regardless of success or failure.

Fixes #7602

scrapy/core/downloader/handlers/ftp.py

@@ -119,7 +119,9 @@ class FTPDownloadHandler(BaseDownloadHandler):
                 httpcode = self.CODE_MAPPING.get(ftpcode, self.CODE_MAPPING["default"])
                 return Response(url=request.url, status=httpcode, body=message.encode())
             raise
-        protocol.close()
+        finally:
+            protocol.close()
+            client.loseConnection()
         headers = {"local filename": protocol.filename or b"", "size": protocol.size}
         body = protocol.filename or protocol.body.read()
         respcls = responsetypes.from_args(url=request.url, body=body)