Stand up open-webui on dankclaw (quadlet, boot-persistent)

Replace the dead dankserver open-webui (bare container, :3000, pointed at a
dead :9090 backend) with a boot-persistent quadlet on dankclaw:
- CPU image (:main); dankclaw is CPU-only, so the :cuda image is wasted.
- Isolated on slirp4netns; publishes 3005 (3000 is Gitea's HTTP port).
- Default LLM backend is the local vLLM on 52625 (frank-default-large).
- Data persists under /home/dank/Containers/open-webui/data.
- Caddy route now proxies to the published LAN port (the container is not on
  Caddy's network).

Also corrects the model/port mapping in the docs: the live state (verified
2026-08-19) is frank-default-large on vLLM :52625 (dankclaw) and
frank-default-small on llama.cpp :7770 (dankserver) — the reverse of the
2026-08-17 note.

dankclaw/Caddyfile

@@ -31,11 +31,13 @@ comfyui.dankclaw.local {
 }
 
 # --- OpenWebUI ---
+# open-webui is a quadlet container on slirp4netns (isolated), so Caddy cannot
+# reach it by container name. Proxy to its published LAN port instead.
 chat.dankclaw.local {
 	basicauth {
 		dank $2a$14$REPLACE_WITH_HASH
 	}
-	reverse_proxy openwebui:8080
+	reverse_proxy 192.168.0.143:3005
 }
 
 # --- Hermes ---