fix: basicauth double-prefix render; open-webui off slirp4netns

basicauth (2026-08-22 incident):
- the Caddyfile template carried its own $2a$14$ prefix and deploy.sh
  substituted the full hash (prefix included), rendering an invalid
  double-prefixed hash. Every basicauth vhost rejected every password
  with 401 and Caddy logged nothing.
- template is now a bare REPLACE_WITH_HASH token; tests pin the render
  contract (no prefix in template; rendered line is exactly 'dank <hash>').

open-webui (2026-08-22 incident):
- its slirp4netns helper process died, leaving the container running
  with only 'lo' in its netns: port 3005 accepted TCP and reset every
  request, so chat served empty responses for ~2 days, unlogged.
- move to a pinned bridge network (systemd-open-webui, 10.89.3.0/24,
  gw 10.89.3.1) — no per-container helper to die.
- LLM endpoint reached via the gateway (host.containers.internal is
  slirp-only): OPENAI_API_BASE_URL=http://10.89.3.1:52625.
- add a quadlet healthcheck: /health (app) + non-loopback interface
  (network liveness; the dead-tap state leaves only 'lo').
- deploy script now copies the .network file too.
- docs updated (OpenWebUI History section, Caddy basic-auth contract).

dankclaw/open-webui/quadlet/open-webui.network

@@ -0,0 +1,29 @@
+# Quadlet network: private bridge for open-webui (rootless).
+#
+# Install path on dankclaw: ~/.config/containers/systemd/open-webui.network
+# Unit name: open-webui-network.service (podman network name: systemd-open-webui)
+#
+# Why a bridge instead of slirp4netns (2026-08-22 incident):
+# slirp4netns runs a user-space helper process per container. When that
+# helper died, the container kept running but lost its tap interface,
+# becoming a zombie that accepted TCP and reset every request. chat
+# served empty responses for ~2 days and nothing logged an error.
+# A kernel bridge has no per-container helper, so the failure mode
+# cannot occur.
+#
+# The subnet is pinned so the gateway IP is deterministic: the LLM
+# backend (llama-server :52625, bound 0.0.0.0 on the host) is reached
+# from the container via the gateway. host.containers.internal is a
+# slirp4netns-only name and does not resolve on a bridge.
+#
+# Subnet registry on dankclaw (rootless):
+#   10.88.0.0/16  default "podman" bridge
+#   10.89.0.0/24  gitea (systemd-gitea)
+#   10.89.1.0/24  compose stack (dankclaw_default)
+#   10.89.2.0/24  searxng (systemd-searxng)
+#   10.89.3.0/24  open-webui (systemd-open-webui)  <- this file
+
+[Network]
+Driver=bridge
+Subnet=10.89.3.0/24
+Gateway=10.89.3.1