revert ubuntu:22.04

Dockerfile.standalone

@@ -3,7 +3,7 @@
 #   1. Local: place files in prebuilt/qemu/ (from build-qemu.sh or manual copy)
 #   2. CI/CD: downloads from GitHub Release (requires qemu-lcgamboa repo to be public)
 # The COPY always runs; the RUN only downloads missing files.
-FROM debian:bookworm-slim AS qemu-provider
+FROM ubuntu:22.04 AS qemu-provider
 
 RUN apt-get update && apt-get install -y --no-install-recommends curl ca-certificates \
     && rm -rf /var/lib/apt/lists/*