Local file overwrite via configuration symlink race

TOCTOU in YtGrabber-TUI 1.0 allows local users to overwrite files accessible to the application through a configuration-file symlink race. In Settings.hpp, load_json_settings checks whether config.json exists before create_json_settings writes it, allowing a symlink inserted between those operations to redirect boost::property_tree::write_json to another file. Exploitation requires write access to the Linux configuration directory or Windows working directory and precise timing; the result is file corruption within the process privileges, including system-file corruption when the application runs elevated.