Upload files to Drive.

Upload one or more files to Drive. - `files`: the file uploads (multipart) - `metadata`: a JSON string containing a list of per-file metadata dicts, positionally aligned with `files`. Each dict may contain: - `path` — fully qualified destination path (takes precedence) - `folder` — destination folder - `name` — destination filename Resolution logic for each file at index i: - If path is provided, use it as the fully qualified path - Else if folder and name are provided, combine as {folder}/{name} - Else if folder is provided, combine as {folder}/{upload_filename} - Else if name is provided, use /{name} (root) - Else fall back to None (domain default behavior)