Add player controller, state management, and input handling

- Implemented PlayerController.cs to manage player movement and actions.
- Created PlayerState.cs to track player lives, coins, and key status.
- Added CameraFollow.cs for smooth camera movement following the player.
- Developed Character.cs as an abstract class for character behavior.
- Introduced Enums.cs for defining TreasureType and MapElementType.
- Added IDoor interface for door interactions.
- Created InputActions.cs for handling player input actions.
- Implemented MainMenu.cs for basic menu functionality including play and exit options.

Assets/Scripts/KeyChest.cs

@@ -1,14 +1,35 @@
-using System.Security;
 using UnityEngine;
 
 public class KeyChest : MonoBehaviour
 {
+    private bool _isOpened = false;
+
     private void OnTriggerEnter2D(Collider2D collider)
     {
+        if (_isOpened)
+            return;
+
         var playerState = collider.GetComponent<PlayerState>();
         if (playerState != null)
         {
+            _isOpened = true;
+
+            // Update player state
             playerState.SetKey();
+
+            // Notify GameManager of key collection
+            if (GameManager.Instance != null)
+            {
+                GameManager.Instance.SetKeyState(true);
+            }
+
+            // Notify LevelManager of key collection
+            if (LevelManager.Instance != null)
+            {
+                LevelManager.Instance.NotifyKeyCollected();
+            }
+
+            // Destroy the chest
             Destroy(gameObject);
         }
     }