fix(iso): replace grub-pc/grub-efi-amd64 with -bin variants to fix package conflict

grub-pc and grub-efi-amd64 conflict with each other in Debian 12.
The -bin packages provide the same grub-install binaries without conflict.

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

iso/builder/config/package-lists/bee.list.chroot

@@ -21,8 +21,8 @@ openssh-server
 # Disk installer
 squashfs-tools
 parted
-grub-pc
-grub-efi-amd64
+grub-pc-bin
+grub-efi-amd64-bin
 
 # Filesystem support for USB export targets
 exfatprogs