fix(ci): add zstd to CI environment for rootfs compression

- Install zstd inline in build-rootfs workflow step (immediate fix)
- Add zstd to CI Dockerfile for future image builds

Author: drew

.github/workflows/release-vm-dev.yml

@@ -155,6 +155,9 @@ jobs:
       - name: Install tools
         run: mise install
 
+      - name: Install zstd
+        run: apt-get update && apt-get install -y --no-install-recommends zstd && rm -rf /var/lib/apt/lists/*
+
       - name: Build base rootfs tarball
         run: |
           set -euo pipefail

deploy/docker/Dockerfile.ci

@@ -34,6 +34,7 @@ RUN apt-get update && apt-get install -y --no-install-recommends \
     xz-utils \
     jq \
     rsync \
+    zstd \
     && apt-get install -y --only-upgrade gpgv python3 \
     && rm -rf /var/lib/apt/lists/*