Replace envsubst with sed in searxng entrypoint to avoid extra dependencies

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

searxng/entrypoint.sh

@@ -1,6 +1,8 @@
 #!/bin/sh
 set -e
 
-envsubst < /searxng/settings.yml.template > /etc/searxng/settings.yml
+sed -e "s|\${BASE_URL}|${BASE_URL}|g" \
+    -e "s|\${SEARXNG_SECRET_KEY}|${SEARXNG_SECRET_KEY}|g" \
+    /searxng/settings.yml.template > /etc/searxng/settings.yml
 
 exec /usr/local/searxng/dockerfiles/docker-entrypoint.sh "$@"