Fix ARM64 Dockerfile: use HTTP for ALARM tarball download

os.archlinuxarm.org has a TLS cert mismatch (cert SAN doesn't cover the
hostname). ALARM officially distributes over HTTP, not HTTPS.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

iso/docker/Dockerfile.arm64

@@ -9,7 +9,7 @@ FROM --platform=linux/arm64 alpine:3.20 AS alarm-fetch
 RUN apk add --no-cache curl libarchive-tools
 
 RUN curl -fL --retry 3 --progress-bar \
-        https://os.archlinuxarm.org/os/ArchLinuxARM-aarch64-latest.tar.gz \
+        http://os.archlinuxarm.org/os/ArchLinuxARM-aarch64-latest.tar.gz \
         -o /tmp/alarm.tar.gz && \
     mkdir /alarm-root && \
     bsdtar -xpf /tmp/alarm.tar.gz -C /alarm-root && \