Replace hidden file inputs and anchor downloads with native open/save
dialogs via a thin platform layer. WAV export sends base64 audio data to
the Go backend for writing to the user-chosen path.
Co-authored-by: Cursor <cursoragent@cursor.com>
FileService exposes open/save dialogs for video, project JSON, and WAV
export. User-selected videos stream from disk at /localmedia/video with
range request support for seeking in the webview.
Co-authored-by: Cursor <cursoragent@cursor.com>
end