Add attribute system with core stats and gameplay components

GameCore/Combat/DamageEventComponent.cs

@@ -0,0 +1,15 @@
+using GameCore.ECS;
+using GameCore.ECS.Interfaces;
+
+namespace GameCore.Combat;
+
+/// <summary>
+///     A temporary, event-like component. When this component is added to an entity,
+///     the DamageSystem will process it, apply damage to the target, and then
+///     immediately remove this component. This simulates a one-time damage event.
+/// </summary>
+public class DamageEventComponent(Entity target, float amount) : IComponent
+{
+    public Entity Target { get; set; } = target;
+    public float Amount { get; set; } = amount;
+}