fancynpcs: Add BetterModel integration

[wiflow]

Summary

• Add optional BetterModel support for rendering custom BlockBench models on NPCs
• New /npc model and /npc animate commands for model management
• Model persistence and automatic spawning/despawning with visibility tracking
• play_animation NPC action for triggering animations via interactions

Features

• /npc model <npc> <model> - Apply or remove BetterModel models to NPCs
• /npc model <npc> eyeheight <height> - Set custom eye height for turn-to-player functionality
• /npc animate <npc> <animation> - Play model animations on NPCs
• Model interaction bridging for click events on model hitboxes
• Prevents incompatible commands (skin, type, scale, showInTab) on NPCs with models

Technical Changes

• BetterModelHook - Runtime availability detection for BetterModel plugin
• NpcModelController - EntityTracker lifecycle management
• ModelInteractionBridge - Event handling for model interactions
• Added getEntity() abstract method to Npc API for model attachment
• Model data persistence in npcs.yml

Test plan

• Install BetterModel and FancyNpcs on a test server
• Create an NPC and apply a model with /npc model <npc> <model>
• Verify model displays correctly and follows NPC visibility
• Test /npc animate command with available animations
• Verify turn-to-player works with custom eye height
• Test model removal with /npc model <npc> @none
• Verify model persistence after server restart
• Test model interaction (clicking on model hitbox triggers NPC actions)
• Confirm incompatible commands are blocked for model NPCs

[NoltoxGit]

If you want to add compatibility with BettModel, please also add compatibility with ModelEngine. Thank you! 🙌