SearXNG: define the gluetun+searxng+valkey trio as quadlet units

Converts the podman-compose SearXNG stack to boot-persistent quadlet units so
it survives a reboot (the compose deployment did not). searxng sets
Network=gluetun.container, which makes it reuse gluetun's network namespace so
outbound search traffic exits the WireGuard tunnel; it publishes no port of its
own (the port lives on gluetun). gluetun and valkey join a pinned searxng
network (10.89.2.0/24, DNS-enabled) so searxng reaches valkey by name.

Secrets stay in /opt/searxng/.env (mode 0600), referenced via [Service]
EnvironmentFile= so ${VAR} expands. Adds a bats seam asserting the netns
wiring, port placement, boot install, and that no secret material is tracked.

dankclaw/searxng/quadlet/searxng-valkey.container

@@ -0,0 +1,28 @@
+# Quadlet unit: Valkey cache for SearXNG (rootless, boot-persistent).
+#
+# Install path on dankclaw: ~/.config/containers/systemd/searxng-valkey.container
+# Unit name: searxng-valkey.service (container name: searxng-valkey)
+#
+# The limiter's rate-limit state store. Joins the searxng network and is
+# reachable by the name "valkey" (settings.yml points there). Data persists in
+# /opt/searxng/valkey. See docs/Dankclaw/Valkey.md.
+
+[Unit]
+Description=SearXNG Valkey cache container
+Wants=searxng-network.service
+After=searxng-network.service network.target
+
+[Container]
+ContainerName=searxng-valkey
+Network=searxng.network
+NetworkAlias=valkey
+Image=docker.io/valkey/valkey:9-alpine
+Volume=/opt/searxng/valkey:/data
+
+[Service]
+EnvironmentFile=/opt/searxng/.env
+TimeoutStartSec=900
+Restart=always
+
+[Install]
+WantedBy=default.target