Fix su invocation in docker-entrypoint.sh causing 502 in prod

su forge -s /bin/sh -c 'exec "$@"' -- "$@" didn't forward gunicorn's
argv correctly with this image's su, so the container never actually
started gunicorn — Caddy then had nothing to proxy to (502). Flatten
the command into a single string via "$*" instead.

docker-entrypoint.sh

@@ -11,4 +11,4 @@ set -e
 mkdir -p /app/projects
 chown -R forge:forge /app/projects
 
-exec su forge -s /bin/sh -c 'exec "$@"' -- "$@"
+exec su forge -s /bin/sh -c "$*"