Fix: use tee for OpenResty keyring and sources.list writes

The echo "..." \ <newline> > file pattern has the backslash consumed
by the Dockerfile parser, leaving a bare redirect that /bin/sh may not
handle reliably. Switch to pipe through tee for both writes.

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

docker/Dockerfile

@@ -59,9 +59,8 @@ RUN set -eux; \
     if [ "$WITH_PSQL_CLIENT" = "1" ]; then apt-get install -y --no-install-recommends postgresql-client; fi; \
     if [ "$WITH_NGINX" = "1" ]; then \
       apt-get install -y --no-install-recommends gnupg; \
-      curl -fsSL https://openresty.org/package/pubkey.gpg | gpg --dearmor -o /usr/share/keyrings/openresty.gpg; \
+      curl -fsSL https://openresty.org/package/pubkey.gpg | gpg --dearmor | tee /usr/share/keyrings/openresty.gpg > /dev/null; \
-      echo "deb [signed-by=/usr/share/keyrings/openresty.gpg] http://openresty.org/package/debian bookworm openresty" \
+      echo "deb [signed-by=/usr/share/keyrings/openresty.gpg] http://openresty.org/package/debian bookworm openresty" | tee /etc/apt/sources.list.d/openresty.list; \
-        > /etc/apt/sources.list.d/openresty.list; \
       apt-get update; \
       apt-get install -y --no-install-recommends openresty libmaxminddb0; \
       opm get anjia0532/lua-resty-maxminddb; \