feat: 투사체 발사 스킬 구현

- SkillProjectile: 서버 권위 이동/충돌, caster 자식 콜라이더 충돌 무시 추가
- SpawnEffect: hitEffect 필드 추가 (투사체 명중 시 적용할 효과 분리)
- SkillEffect: Team 컴포넌트 없는 환경 오브젝트 타겟 제외 처리
- Prefab_Skill_ProjectileBasic 프리팹 생성 (NetworkObject + NetworkTransform + Rigidbody + SphereCollider)
- 투사체 스킬 에셋 추가 (SkillData, SpawnEffect, DamageEffect)
- Anim_Common_찌르기 애니메이션 이벤트 추가 (OnEffect @ 0.867s, OnSkillEnd @ 1.3s)
- DefaultNetworkPrefabs에 Prefab_Skill_ProjectileBasic 등록

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

Assets/_Game/Prefabs/Player/Prefab_Player_Default.prefab

@@ -295,7 +295,8 @@ MonoBehaviour:
   animator: {fileID: 3426985706796420257}
   baseController: {fileID: 9100000, guid: db718381bb2992e469c76c64015e065b, type: 2}
   baseSkillClip: {fileID: -7717634560727564301, guid: 0f6fd9302e489b94d96774e2713b1317, type: 3}
-  registeredClips: []
+  registeredClips:
+  - {fileID: -8689311932429934276, guid: ac0adc4c7f982fe4d82eac9c2267f0c6, type: 3}
   debugMode: 1
   showAreaDebug: 1
   debugDrawDuration: 1
@@ -314,7 +315,7 @@ MonoBehaviour:
   ShowTopMostFoldoutHeaderGroup: 1
   skillSlots:
   - {fileID: 11400000, guid: b7f09e0e899c8fc4bb2cc9204cc6eb4a, type: 2}
-  - {fileID: 0}
+  - {fileID: 11400000, guid: b8c86399865e91144a3d6fcfddc04fd9, type: 2}
   - {fileID: 0}
   - {fileID: 0}
   - {fileID: 0}