infra: container-only workflow (packaging image + scripts); README: add No Host Pollution policy

scripts/packaging-up.sh

@@ -0,0 +1,30 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+NAME=${PACKAGING_CONTAINER_NAME:-tsys-cloudron-packaging}
+IMAGE=${PACKAGING_IMAGE:-knel/packaging:latest}
+DOCKERFILE=${PACKAGING_DOCKERFILE:-docker/packaging/Dockerfile}
+
+if ! docker image inspect "$IMAGE" >/dev/null 2>&1; then
+  echo "Building packaging image: $IMAGE"
+  docker build -t "$IMAGE" -f "$DOCKERFILE" .
+fi
+
+if ! docker ps -a --format '{{.Names}}' | grep -qx "$NAME"; then
+  echo "Creating container: $NAME"
+  docker run -d \
+    --name "$NAME" \
+    -v "$PWD":/workspace \
+    -w /workspace \
+    -v /var/run/docker.sock:/var/run/docker.sock \
+    "$IMAGE"
+else
+  # Ensure it is running
+  if ! docker ps --format '{{.Names}}' | grep -qx "$NAME"; then
+    echo "Starting container: $NAME"
+    docker start "$NAME"
+  fi
+fi
+
+echo "Packaging container ready: $NAME (image: $IMAGE)"
+