fix: Remove 60 MB (28%) of dev dependencies from Docker image (#28160)

docker/Dockerfile

@@ -13,11 +13,14 @@ COPY package.json pnpm-lock.yaml ./
 
 # Make and such are needed to compile serialport for riscv64
 # Install pnpm, configure a tmp-based store, then use it under a cache mount so each arch gets its own store
+# NOTE: We do not install devDependencies here (the --prod argument in pnpm install) as we use an already
+#       built artifact (./dist directory) from previous GitHub runner stages.  Omitting devDependencies here
+#       saves storage as this node_modules/ is being copied straight to the release stage later.
 RUN --mount=type=cache,id=pnpm-store,target=/tmp/pnpm-store \
     apk add --no-cache make gcc g++ python3 linux-headers npm && \
     npm install -g pnpm@$(sed -n 's/.*"packageManager": "pnpm@\([0-9.]*\)".*/\1/p' package.json) && \
     pnpm config set store-dir /tmp/pnpm-store && \
-    pnpm install --frozen-lockfile --no-optional && \
+    pnpm install --frozen-lockfile --prod --no-optional && \
     # serialport has outdated prebuilds that appear to fail on some archs, force build on target platform
     rm -rf $(find ./node_modules/.pnpm/ -wholename "*/@serialport/bindings-cpp/prebuilds" -type d) && \
     pnpm rebuild @serialport/bindings-cpp