feat(dcgm): add NVIDIA DCGM diagnostics, fix KVM console

- Add 9002-nvidia-dcgm.hook.chroot: installs datacenter-gpu-manager
  from NVIDIA apt repo during live-build
- Enable nvidia-dcgm.service in chroot setup hook
- Replace bee-gpu-stress with dcgmi diag (levels 1-4) in NVIDIA SAT
- TUI: replace GPU checkbox + duration UI with DCGM level selection
- Remove console=tty2 from boot params: KVM/VGA now shows tty1
  where bee-tui runs, fixing unresponsive console

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

iso/builder/config/hooks/normal/9000-bee-setup.hook.chroot

@@ -21,6 +21,7 @@ ensure_bee_console_user() {
 ensure_bee_console_user
 
 # Enable bee services
+systemctl enable nvidia-dcgm.service 2>/dev/null || true
 systemctl enable bee-network.service
 systemctl enable bee-nvidia.service
 systemctl enable bee-preflight.service