feat(pet): add Hey Hey chicken pet addon

Tameable white chicken modelled on Hey Hey from Moana — custom plump
geometry, waddly walk/peck animations, hatching egg item, and vanilla
chicken sounds. Mounted on all 4 servers via docker-compose.

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

addon/heyhe_pet_RP/texts/en_US.lang

@@ -0,0 +1,5 @@
+entity.silverlabs:heyhe_chicken.name=Hey Hey
+entity.silverlabs:heyhe_egg.name=Hey Hey's Egg
+item.silverlabs:heyhe_egg.name=Hey Hey's Egg
+action.interact.tame=Tame with Food
+action.interact.sit=Sit / Stand