Adds --urls-file so a run can reference a hand-maintained list rather
than repeating --profile, which is how this actually gets used: the
ARTMS accounts now live in artms_account_links.txt at the archive root.
The parser takes what a person would paste. Full URLs, scheme-less URLs
and bare usernames all work; blank lines and # comments are ignored and
duplicates dropped, so the list can be appended to carelessly. Lines that
are not profiles are rejected loudly rather than silently syncing
nothing: an Instagram post URL yields the segment "p", which would
otherwise be treated as a username and create a directory called "p".
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>