[Skills] 부채꼴 범위 판정 및 디버그 시각화 추가

- AreaShapeType enum 추가 (Sphere, Fan)
- 부채꼴 설정: 원점 거리, 반지름, 좌우 각도
- 런타임 범위 시각화 (Scene 뷰)
- 스킬 에셋 파일 구조 정리

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