feat: host-derived nicks and generic identity

Nick is now deterministically generated from the exit endpoint
hostname via seeded markov chain. Same exit IP always produces the
same nick. Config nick field is optional fallback only.

Registration uses generic ident (user/ident) and realname
(realname/unknown) instead of random markov words.

Also fixes compose env vars and build target to use podman-compose.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

compose.yaml

@@ -8,6 +8,10 @@ services:
     network_mode: host
     logging:
       driver: k8s-file
+    environment:
+      PYTHONUNBUFFERED: "1"
+      PYTHONDONTWRITEBYTECODE: "1"
+      PYTHONPATH: /app/src
     volumes:
       - ./src:/app/src:Z,ro
       - ./config:/data:Z