feat: custom base image to pre-bake apt updates

docker/base.Dockerfile

@@ -0,0 +1,16 @@
+FROM node:24-slim AS base
+
+# Pre-bake OS updates and common packages shared across all apps.
+# Rebuild this image weekly or when base packages change.
+# Push to: git.mosaicstack.dev/mosaic/node-base:24-slim
+RUN apt-get update && apt-get upgrade -y --no-install-recommends \
+    && apt-get install -y --no-install-recommends \
+        openssl \
+        ca-certificates \
+        curl \
+        dumb-init \
+    && apt-get clean \
+    && rm -rf /var/lib/apt/lists/*
+
+# Enable corepack for pnpm
+RUN corepack enable