Process users one at a time through the whole pipeline, added --queue [file] and --wait. Fixed self posts never being saved.

Users now go through profile, posts, content info and downloads one by one (preparing the next
user while the current one downloads), saving each index as soon as that user is done. The queue
is re-read between users, users are removed once archived, and a lock file lets a second
--queue invocation hand its users to the running process.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

.gitignore

@@ -7,3 +7,4 @@ dist/
 users*
 posts
 ignore
+/queue*