feat: 플레이어 사망 및 리스폰 시스템 구현

- isDead 네트워크 변수 추가로 사망 상태 동기화
- 사망 시 이동/스킬 비활성화 및 사망 애니메이션 재생
- Respawn() 메서드로 체력/마나 회복 및 컴포넌트 재활성화
- 스킬 입력에서 사망 상태 체크 추가

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-opencode)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

Assets/Scripts/Player/PlayerNetworkController.cs

@@ -18,6 +18,7 @@ namespace Colosseum.Player
         // 네트워크 동기화 변수
         private NetworkVariable<float> currentHealth = new NetworkVariable<float>(100f);
         private NetworkVariable<float> currentMana = new NetworkVariable<float>(50f);
+        private NetworkVariable<bool> isDead = new NetworkVariable<bool>(false);
 
         public float Health => currentHealth.Value;
         public float Mana => currentMana.Value;
@@ -29,9 +30,13 @@ namespace Colosseum.Player
         public event Action<float, float> OnHealthChanged; // (oldValue, newValue)
         public event Action<float, float> OnManaChanged; // (oldValue, newValue)
 
+        // 사망 이벤트
+        public event Action<PlayerNetworkController> OnDeath;
+        public event Action<bool> OnDeathStateChanged; // (isDead)
+
         // IDamageable 구현
         public float CurrentHealth => currentHealth.Value;
-        public bool IsDead => currentHealth.Value <= 0f;
+        public bool IsDead => isDead.Value;
 
         public override void OnNetworkSpawn()
         {
@@ -44,12 +49,14 @@ namespace Colosseum.Player
             // 네트워크 변수 변경 콜백 등록
             currentHealth.OnValueChanged += HandleHealthChanged;
             currentMana.OnValueChanged += HandleManaChanged;
+            isDead.OnValueChanged += HandleDeathStateChanged;
 
             // 초기화
             if (IsServer)
             {
                 currentHealth.Value = MaxHealth;
                 currentMana.Value = MaxMana;
+                isDead.Value = false;
             }
         }
 
@@ -58,6 +65,7 @@ namespace Colosseum.Player
             // 콜백 해제
             currentHealth.OnValueChanged -= HandleHealthChanged;
             currentMana.OnValueChanged -= HandleManaChanged;
+            isDead.OnValueChanged -= HandleDeathStateChanged;
         }
 
         private void HandleHealthChanged(float oldValue, float newValue)
@@ -70,12 +78,19 @@ namespace Colosseum.Player
             OnManaChanged?.Invoke(oldValue, newValue);
         }
 
+        private void HandleDeathStateChanged(bool oldValue, bool newValue)
+        {
+            OnDeathStateChanged?.Invoke(newValue);
+        }
+
         /// <summary>
         /// 대미지 적용 (서버에서만 실행)
         /// </summary>
         [Rpc(SendTo.Server)]
         public void TakeDamageRpc(float damage)
         {
+            if (isDead.Value) return;
+
             currentHealth.Value = Mathf.Max(0f, currentHealth.Value - damage);
 
             if (currentHealth.Value <= 0f)
@@ -111,10 +126,75 @@ namespace Colosseum.Player
             currentMana.Value = Mathf.Min(MaxMana, currentMana.Value + amount);
         }
 
+        /// <summary>
+        /// 사망 처리 (서버에서만 실행)
+        /// </summary>
         private void HandleDeath()
         {
-            // TODO: 사망 처리 로직
-            Debug.Log($"Player {OwnerClientId} died!");
+            if (isDead.Value) return;
+
+            isDead.Value = true;
+
+            // 이동 비활성화
+            var movement = GetComponent<PlayerMovement>();
+            if (movement != null)
+            {
+                movement.enabled = false;
+            }
+
+            // 스킬 입력 비활성화
+            var skillInput = GetComponent<PlayerSkillInput>();
+            if (skillInput != null)
+            {
+                skillInput.enabled = false;
+            }
+
+            // 사망 애니메이션 재생
+            var animator = GetComponentInChildren<Animator>();
+            if (animator != null)
+            {
+                animator.SetTrigger("Die");
+            }
+
+            // 사망 이벤트 발생
+            OnDeath?.Invoke(this);
+
+            Debug.Log($"[Player] Player {OwnerClientId} died!");
+        }
+
+        /// <summary>
+        /// 리스폰 (서버에서만 실행)
+        /// </summary>
+        public void Respawn()
+        {
+            if (!IsServer) return;
+
+            isDead.Value = false;
+            currentHealth.Value = MaxHealth;
+            currentMana.Value = MaxMana;
+
+            // 이동 재활성화
+            var movement = GetComponent<PlayerMovement>();
+            if (movement != null)
+            {
+                movement.enabled = true;
+            }
+
+            // 스킬 입력 재활성화
+            var skillInput = GetComponent<PlayerSkillInput>();
+            if (skillInput != null)
+            {
+                skillInput.enabled = true;
+            }
+
+            // 애니메이션 리셋
+            var animator = GetComponentInChildren<Animator>();
+            if (animator != null)
+            {
+                animator.Rebind();
+            }
+
+            Debug.Log($"[Player] Player {OwnerClientId} respawned!");
         }
 
         #region IDamageable
@@ -123,7 +203,7 @@ namespace Colosseum.Player
         /// </summary>
         public float TakeDamage(float damage, object source = null)
         {
-            if (!IsServer) return 0f;
+            if (!IsServer || isDead.Value) return 0f;
 
             float actualDamage = Mathf.Min(damage, currentHealth.Value);
             currentHealth.Value = Mathf.Max(0f, currentHealth.Value - damage);
@@ -141,7 +221,7 @@ namespace Colosseum.Player
         /// </summary>
         public float Heal(float amount)
         {
-            if (!IsServer) return 0f;
+            if (!IsServer || isDead.Value) return 0f;
 
             float actualHeal = Mathf.Min(amount, MaxHealth - currentHealth.Value);
             currentHealth.Value = Mathf.Min(MaxHealth, currentHealth.Value + amount);