BetterPets-Paper

Fix: Skins are now yours, not the pet's

Unlocked cosmetic variants are now collected per player (per pet type) instead of being stored on the individual owned pet.

• Scrapping a pet's skin unlocks it for you regardless of whether you own that pet, and it stays in your collection even if you later scrap all your copies.
• The Customize menu and skin-swapping read from your personal collection.
• Existing data migrates automatically — your pets' current skins and previously unlocked variants are moved into your per-player collection on first load.

Compiles clean on Paper 26.2; 63/63 tests pass. Drop BetterPets-1.17.3.jar into your plugins/ folder.