fix: add gnupg for caddy repo key import

Dockerfile

@@ -13,7 +13,7 @@ ARG III_SDK_VERSION=0.11.2
 RUN apt-get update \
     && apt-get install -y --no-install-recommends \
        debian-keyring debian-archive-keyring apt-transport-https \
-       curl openssl ca-certificates tini gosu python3 python3-pip \
+       curl gnupg openssl ca-certificates tini gosu python3 python3-pip \
     && curl -1sLf 'https://dl.cloudsmith.io/public/caddy/stable/gpg.key' \
        | gpg --dearmor -o /usr/share/keyrings/caddy-stable-archive-keyring.gpg \
     && curl -1sLf 'https://dl.cloudsmith.io/public/caddy/stable/debian.deb.txt' \