fix(hint): explain that "--force" option exists

[oleksandr-nc]

Fixes #624

When the occ app_api:app:unregister command fails to remove a container (e.g., because it was already deleted manually), users are now shown a helpful hint suggesting the --force option to continue unregistering.

The hint includes the container name for easier manual verification/cleanup.

Before:

  Failed to remove ExApp my_ex_app container

After:

  Failed to remove ExApp my_ex_app container
  Hint: If the container "nc_app_my_ex_app" was already removed manually, you can use the --force option to continue unregistering.