Add pl8list infinite-scroll app with pl8list sign-in

Endless TikTok-style feed over pl8list's Remix loaders. A guest crawler
builds a shared catalogue; a per-user ranker learns from likes, full
listens and skips. Users sign in with pl8list's email code; only a hash
of the local session token is stored. Ships as a hardened Docker image
with a Traefik override for pl8.narl.io.

.dockerignore

@@ -0,0 +1,9 @@
+.git
+.env
+*.db
+*.db-*
+__pycache__/
+docs/
+README.md
+compose*.yaml
+Dockerfile