Command: ddev exec php artisan test --filter='blocks active duplicate ccli_id with DuplicateCcliSongException'

PASS: Active duplicate CCLI-ID is blocked.

Verified assertions:
- first import succeeds
- second import throws App\Exceptions\DuplicateCcliSongException
- exception existingSongId matches original Song ID
- exception message contains "existiert bereits"
- Song::count() remains 1
