revert(iso): remove apt-cacher-ng support, use lb package cache instead

apt-cacher-ng requires a separate container; lb's own package cache
persisted in --cache-dir is simpler and sufficient.

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

iso/builder/auto/config

@@ -16,14 +16,6 @@ else
     LB_LINUX_PACKAGES="linux-image"
 fi
 
-# Route apt through proxy if BEE_APT_PROXY is set (e.g. apt-cacher-ng).
-# Usage: APT_PROXY=http://host:3142 ./build-in-container.sh
-if [ -n "${BEE_APT_PROXY:-}" ]; then
-    _MIRROR="${BEE_APT_PROXY%/}/debian"
-else
-    _MIRROR="https://deb.debian.org/debian"
-fi
-
 lb config noauto \
     --distribution bookworm \
     --architectures amd64 \
@@ -31,9 +23,9 @@ lb config noauto \
     --bootloaders "grub-efi,syslinux" \
     --debian-installer none \
     --archive-areas "main contrib non-free non-free-firmware" \
-    --mirror-bootstrap "${_MIRROR}" \
-    --mirror-chroot "${_MIRROR}" \
-    --mirror-binary "${_MIRROR}" \
+    --mirror-bootstrap "https://deb.debian.org/debian" \
+    --mirror-chroot "https://deb.debian.org/debian" \
+    --mirror-binary "https://deb.debian.org/debian" \
     --security true \
     --linux-flavours "amd64" \
     --linux-packages "${LB_LINUX_PACKAGES}" \

iso/builder/build-in-container.sh

@@ -9,7 +9,6 @@ CONTAINER_TOOL="${CONTAINER_TOOL:-docker}"
 IMAGE_TAG="${BEE_BUILDER_IMAGE:-bee-iso-builder}"
 BUILDER_PLATFORM="${BEE_BUILDER_PLATFORM:-linux/amd64}"
 CACHE_DIR="${BEE_BUILDER_CACHE_DIR:-${REPO_ROOT}/dist/container-cache}"
-APT_PROXY="${APT_PROXY:-}"
 AUTH_KEYS=""
 REBUILD_IMAGE=0
 
@@ -29,13 +28,9 @@ while [ $# -gt 0 ]; do
             AUTH_KEYS="$2"
             shift 2
             ;;
-        --apt-proxy)
-            APT_PROXY="$2"
-            shift 2
-            ;;
         *)
             echo "unknown arg: $1" >&2
-            echo "usage: $0 [--cache-dir /path] [--rebuild-image] [--authorized-keys /path/to/authorized_keys] [--apt-proxy http://host:3142]" >&2
+            echo "usage: $0 [--cache-dir /path] [--rebuild-image] [--authorized-keys /path/to/authorized_keys]" >&2
             exit 1
             ;;
     esac
@@ -105,7 +100,6 @@ set -- \
     -e GOMODCACHE=/cache/go-mod \
     -e TMPDIR=/cache/tmp \
     -e BEE_CACHE_DIR=/cache/bee \
-    ${APT_PROXY:+-e BEE_APT_PROXY="${APT_PROXY}"} \
     -w /work \
     "${IMAGE_REF}" \
     sh /work/iso/builder/build.sh
@@ -121,7 +115,6 @@ if [ -n "$AUTH_KEYS" ]; then
         -e GOMODCACHE=/cache/go-mod \
         -e TMPDIR=/cache/tmp \
         -e BEE_CACHE_DIR=/cache/bee \
-        ${APT_PROXY:+-e BEE_APT_PROXY="${APT_PROXY}"} \
         -w /work \
         "${IMAGE_REF}" \
         sh /work/iso/builder/build.sh --authorized-keys "/tmp/bee-authkeys/${AUTH_KEYS_BASE}"