CTAO Science Portal: static Astro site with git-based CMS (Sveltia + Gitea)

Portal code only; editorial content lives in the ctao/content repo on the
demo machine's Gitea and is overlaid at build time (see README.md and
deploy/README.md). Live demo: https://astro.isl-dev.grid.cyfronet.pl

deploy/Containerfile.build

@@ -0,0 +1,8 @@
+# Build image for the CTAO portal demo: pinned Node + git.
+# Why: the host has node 24 but NO git (and we have no sudo); a 2-line image
+# keeps node pinned and independent of host packages (git comes from the
+# alpine repo unpinned — alpine drops old package versions, pinning is moot).
+# Built ONCE at install, never pulled again at runtime:
+#   podman build -t localhost/ctao-portal-build:1 -f Containerfile.build .
+FROM docker.io/library/node:24-alpine@sha256:a0b9bf06e4e6193cf7a0f58816cc935ff8c2a908f81e6f1a95432d679c54fbfd
+RUN apk add --no-cache git