Worked on the upload stuff. It works, but the SD card seems to die after a few MB... :-/

include/http_server.h

@@ -16,6 +16,7 @@ private:
 	void _handle_upload(AsyncWebServerRequest* request, String filename, size_t index, uint8_t* data, size_t len, bool final);
 	uint16_t _chunk_length;
 	uint8_t* _chunk;
+	File _upload_file;
 	uint32_t _file_size;
 	uint32_t _file_size_done;
 	bool _need_header;