AddonSpawner List Generation - Multi-Vehicle Pack Fix

Fixed AddonSpawner .list file generation for multi-vehicle packs, which previously only worked for single vehicles and DLC merge operations.

The list now correctly filters out tuning parts (wheels, bumpers, spoilers, etc.) and only includes main vehicle spawn names. Added a confirmation section in the auto-installation completion dialog that shows the created .list file path with an "Open .list" button for quick access.

All tuning parts remain properly included in the DLC conversion files - they're just excluded from the spawn list as intended.