feat: flatten output into variants/ and intermediates/

Drop per-job subdirs for phone-friendly Syncthing layout with
stem-suffixed filenames; keep web state in meta/.

Co-authored-by: Cursor <cursoragent@cursor.com>

compose.yml

@@ -2,8 +2,8 @@
 #
 # worker + web share one host directory (Syncthing share root):
 #   ${DATA_HOST_DIR:-/home/frank/sync.schwenk.online/data/livef12} -> /data
-#   worker watches /data/incoming, writes /data/jobs
-#   web reads jobs, writes remix variants
+#   worker watches /data/incoming, writes /data/variants + /data/intermediates
+#   web reads meta/ + image dirs, writes remix variants
 #
 # Syncthing itself runs on the host (not in this compose). Copy .env.example
 # to .env for local overrides (e.g. DATA_HOST_DIR=./data). Never commit .env.