feat: enable host network access during Docker build stages for dependency downloads

Add BuildKit syntax directive and --network=host flag to npm install, go mod operations, and apk package installation to allow direct host network access during builds, bypassing Docker's default bridge network for improved reliability and performance of dependency downloads.

deploy/gateway/Dockerfile

@@ -1,6 +1,7 @@
+## syntax=docker/dockerfile:1.4
 FROM alpine:3.21
 
-RUN set -eux; \
+RUN --network=host set -eux; \
     printf '%s\n' \
       'https://dl-cdn.alpinelinux.org/alpine/v3.21/main' \
       'https://dl-cdn.alpinelinux.org/alpine/v3.21/community' \