Prune legacy void/alpine + customize.sh flows

The golden-image Dockerfile + catalog pipeline replaces the entire
manual rootfs-build stack. With that shipped, the per-distro shell
flows are dead code.

Removed:
- scripts/customize.sh, scripts/interactive.sh, scripts/verify.sh
- scripts/make-rootfs{,-void,-alpine}.sh
- scripts/register-{void,alpine}-image.sh
- scripts/make-{void,alpine}-kernel.sh
- internal/imagepreset/ (only consumer was `banger internal packages`,
  which fed customize.sh)
- examples/{void,alpine}.config.toml
- Makefile targets: rootfs, rootfs-void, rootfs-alpine, void-kernel,
  alpine-kernel, void-register, alpine-register, void-vm, alpine-vm,
  verify-void, verify-alpine, plus the ALPINE_RELEASE / *_IMAGE_NAME
  / *_VM_NAME variables

The void-6.12 kernel catalog entry is also gone — golden image pairs
with generic-6.12 and nothing else in the catalog depended on it.

Consolidated: imagemgr now holds the small DebianBasePackages list +
package-hash helper inline, so the `image build --from-image` flow
(still supported) no longer pulls from a separate imagepreset package.

Net: 3,815 lines deleted, 59 added. No runtime functionality removed
beyond the `banger internal packages` subcommand (hidden, used only
by the deleted customize.sh).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

internal/daemon/images.go

@@ -11,7 +11,6 @@ import (
 
 	"banger/internal/api"
 	"banger/internal/daemon/imagemgr"
-	"banger/internal/imagepreset"
 	"banger/internal/kernelcat"
 	"banger/internal/model"
 	"banger/internal/system"
@@ -86,7 +85,7 @@ func (d *Daemon) BuildImage(ctx context.Context, params api.ImageBuildParams) (i
 	if err != nil {
 		return model.Image{}, err
 	}
-	packages := imagepreset.DebianBasePackages()
+	packages := imagemgr.DebianBasePackages()
 	metadataPackages := imagemgr.BuildMetadataPackages(params.Docker)
 	spec := imageBuildSpec{
 		ID:            id,