fix(docker): clear build cache on every build to stop unbounded disk growth

scripts/ci-deploy.sh

@@ -74,6 +74,11 @@ pnpm install --frozen-lockfile
 pnpm exec playwright install chromium
 
 echo "Building $image"
+# Throw away the previous build cache before each build so disk usage doesn't
+# grow unbounded across deployments. The current release image (`epicnext-cms`)
+# is still reused as a base layer via `--cache-from`; only the accumulated
+# BuildKit intermediate cache is discarded.
+docker builder prune -af --filter "until=1h" --keep-storage=0 2>/dev/null || true
 DOCKER_BUILDKIT=1 docker build --network=host --progress=plain --cache-from epicnext-cms:latest \
   --build-arg NEXT_DEPLOYMENT_ID="$sha" -t "$image" .
 check_current

scripts/docker-update.sh

@@ -79,6 +79,9 @@ fi
 log "Node major gate OK (major=${float_major:-?})"
 
 # --- 4. Rebuild the image ---
+# Reset the BuildKit cache first so the build doesn't accumulate unbounded
+# layers on disk across daily rebuilds.
+docker builder prune -af --filter "until=1h" --keep-storage=0 2>>"$LOG_FILE" || true
 docker compose build >>"$LOG_FILE" 2>&1 || die "docker compose build failed" 2
 log "docker compose build OK"