Add LevelUpHud and UpgradeManager components; implement upgrade selection UI and item management

Assets/Scripts/UI/UpgradeSlot.cs

@@ -0,0 +1,54 @@
+using Inventory;
+using Shop;
+using Systems;
+using TMPro;
+using UnityEngine;
+using UnityEngine.UI;
+
+namespace UI
+{
+    public class UpgradeSlot : MonoBehaviour
+    {
+        private UpgradeManager upgradeManager;
+        private ScriptableObject item;
+        
+        [SerializeField] private Image icon;
+        [SerializeField] private TextMeshProUGUI nameText;
+        [SerializeField] private TextMeshProUGUI descriptionText;
+        [SerializeField] private Button selectButton;
+        
+        public void Setup(StatModifierItem item, UpgradeManager manager)
+        {
+            this.item = item;
+            upgradeManager = manager;
+
+            icon.sprite = item.icon;
+            nameText.text = item.name;
+            descriptionText.text = item.description;
+            
+            selectButton.interactable = !upgradeManager.HasSelectedUpgrade;
+            selectButton.onClick.AddListener(() => upgradeManager.SelectUpgrade(item));
+        }
+        
+        public void Setup(WeaponItem weapon, UpgradeManager manager)
+        {
+            item = weapon;
+            upgradeManager = manager;
+            
+            icon.sprite = weapon.icon;
+            nameText.text = weapon.weaponName;
+            descriptionText.text = weapon.description;
+            
+            selectButton.interactable = !upgradeManager.HasSelectedUpgrade;
+            selectButton.onClick.AddListener(() => upgradeManager.SelectUpgrade(weapon));
+        }
+        
+        public bool MatchesItem(ScriptableObject item) => this.item == item;
+
+        public void MarkAsSelected()
+        {
+            selectButton.interactable = false;
+            selectButton.GetComponentInChildren<TextMeshProUGUI>().text = "Selected";
+        }
+    }
+}