ci: the integration job removes its stacks even when the runner kills it

The platform's rule (its ci-sweep.sh, docs/development/security.md),
applied to the one Signage job that starts Docker stacks:
- it has its own EKKLESIA_CI_JOB_KEY;
- it sweeps stale CI stacks from the runner before it starts;
- it removes its own stacks in a final `if: always()` step, which
  tolerates a failed assembly, since nothing was started then;
- the image ci/integration.sh builds is named and labeled as a CI stack
  of this run and job, with the time CI built it, so the sweep finds it.

ci/platform.env moves to the platform commit that adds the sweep
(Ekklesia #60). The assembled lockfile is unchanged, and still passes a
frozen install.

Verified: SIGKILL of the integration script's whole process group
mid-run left 11 resources (2 containers, 4 networks, 4 volumes and the
image). `ci-sweep.sh --job` removed exactly those 11. A normal run
passes, and the job sweep after it finds nothing.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

ci/integration.sh

@@ -15,7 +15,12 @@ workspace="$root/build/workspace"
   exit 1
 }
 
-image="signage-ci:${GITHUB_SHA:-local}-${GITHUB_RUN_ID:-0}-${GITHUB_RUN_ATTEMPT:-1}"
+# Named and labeled as a CI stack of this run and job (the platform's scripts/lib/ci-project.sh), so
+# the workflow's final `ci-sweep.sh --job` removes it even if this script is killed before its trap.
+# shellcheck source=/dev/null
+source "$workspace/scripts/lib/ci-project.sh"
+project="$(ci_project_name signage-image)"
+image="${project}:latest"
 trap 'docker image rm --force "$image" >/dev/null 2>&1 || true' EXIT
 
 scenarios="$(sed -e 's/#.*//' -e '/^[[:space:]]*$/d' "$root/ci/display-scenarios" | tr '\n' ' ')"
@@ -25,6 +30,7 @@ scenarios="$(sed -e 's/#.*//' -e '/^[[:space:]]*$/d' "$root/ci/display-scenarios
 }
 
 DOCKER_BUILDKIT=1 docker build --quiet --file "$workspace/deploy/Dockerfile" --tag "$image" \
+  --label "${EKKLESIA_CI_LABEL}=${project}" --label "${EKKLESIA_CI_CREATED_LABEL}=$(date +%s)" \
   "$workspace" >/dev/null
 echo "integration: built the deployment image with Signage; scenarios: ${scenarios}"