chore: Assets 디렉토리 구조 정리 및 네이밍 컨벤션 적용

- Assets/_Game/ 하위로 게임 에셋 통합
- External/ 패키지 벤더별 분류 (Synty, Animations, UI)
- 에셋 네이밍 컨벤션 확립 및 적용
  (Data_Skill_, Data_SkillEffect_, Prefab_, Anim_, Model_, BT_ 등)
- pre-commit hook으로 네이밍 컨벤션 자동 검사 추가
- RESTRUCTURE_CHECKLIST.md 작성

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

Assets/_Game/Scripts/Skills/Effects/KnockbackEffect.cs

@@ -0,0 +1,30 @@
+using UnityEngine;
+
+namespace Colosseum.Skills.Effects
+{
+    /// <summary>
+    /// 넉백 효과
+    /// </summary>
+    [CreateAssetMenu(fileName = "KnockbackEffect", menuName = "Colosseum/Skills/Effects/Knockback")]
+    public class KnockbackEffect : SkillEffect
+    {
+        [Header("Knockback Settings")]
+        [Min(0f)] [SerializeField] private float force = 5f;
+        [SerializeField] private float upwardForce = 2f;
+
+        protected override void ApplyEffect(GameObject caster, GameObject target)
+        {
+            if (target == null || caster == null) return;
+
+            Vector3 direction = target.transform.position - caster.transform.position;
+            direction.y = 0f;
+            direction.Normalize();
+
+            Vector3 knockback = direction * force + Vector3.up * upwardForce;
+
+            // TODO: 실제 물리 시스템 연동
+            // if (target.TryGetComponent<Rigidbody>(out var rb))
+            //     rb.AddForce(knockback, ForceMode.Impulse);
+        }
+    }
+}