Add Shop system with ShopManager, ShopUI, and ShopSlotUI; implement item purchasing and shop UI functionality

Assets/Scripts/Shop/ShopSlotUI.cs

@@ -0,0 +1,56 @@
+using Inventory;
+using Systems;
+using TMPro;
+using UnityEngine;
+using UnityEngine.UI;
+
+namespace Shop
+{
+    public class ShopSlotUI : MonoBehaviour
+    {
+        private ScriptableObject item;
+        private ShopManager shopManager;
+        private int price;
+        
+        [SerializeField] private Image icon;
+        [SerializeField] private TextMeshProUGUI nameText;
+        [SerializeField] private TextMeshProUGUI descriptionText;
+        [SerializeField] private TextMeshProUGUI priceText;
+        [SerializeField] private Button purchaseButton;
+        
+        public void Setup(StatModifierItem item, ShopManager manager)
+        {
+            this.item = item;
+            shopManager = manager;
+            price = item.price;
+
+            icon.sprite = item.icon;
+            nameText.text = item.name;
+            descriptionText.text = item.description;
+            priceText.text = $"Price: {price}";
+
+            purchaseButton.interactable = GameManager.Instance.Coins >= price;
+            purchaseButton.onClick.AddListener(() => shopManager.BuyItem(item, price));
+        }
+        
+        public void Setup(WeaponItem weapon, ShopManager manager)
+        {
+            item = weapon;
+            shopManager = manager;
+            price = weapon.price;
+            icon.sprite = weapon.icon;
+            nameText.text = weapon.weaponName;
+            descriptionText.text = weapon.description;
+            priceText.text = $"Price: {price}";
+            purchaseButton.interactable = GameManager.Instance.Coins >= price;
+            purchaseButton.onClick.AddListener(() => shopManager.BuyWeapon(weapon, price));
+        }
+
+        public bool MatchesItem(ScriptableObject item) => this.item == item;
+
+        public void MarkAsPurchased()
+        {
+            purchaseButton.interactable = false;
+        }
+    }
+}