Enable boot.loader.initScript for LXC targets

LXC containers share the host kernel — Proxmox starts them by exec'ing
/sbin/init directly in the container's rootfs, no bootloader or initrd
involved at all. Without boot.loader.initScript.enable, that file
isn't wired to launch the current generation, so even a correctly
installed system (see the nix-auto-installer bind-mount fix, same
underlying issue) could still fail to come up after reboot. This is
exactly what nixpkgs' own virtualisation/proxmox-lxc.nix module sets
for the same reason.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

modules/platforms/lxc.nix

@@ -5,4 +5,10 @@
 
   boot.loader.grub.enable = false;
   boot.loader.systemd-boot.enable = false;
+
+  # LXC containers share the host kernel — Proxmox starts them by exec'ing
+  # /sbin/init directly, no bootloader/initrd involved. Without this, that
+  # file doesn't correctly launch the current generation, so even a
+  # correctly-installed system can fail to come up after reboot.
+  boot.loader.initScript.enable = true;
 }